GTX 970 Issue

Which PSU do you have?

Which PSU do you have?

Googled about it, looks like a bad company PSU. Get a better PSU that's Tier 1/2.

PSU Tier list
http://www.tomshardware.com/forum/id-2547993/psu-tier-list.html

I have a similar system (Z97 + i5-4690K + 16GB RAM) and had a similar problem when I had a GTX 970.
It turned out that the 970 was running out of the 3.5GB VRAM.
Due to a buggy game that would not clear the memory after it used it.

I could see a similar problem happening with 3 monitors. More monitors use more VRAM.
While getting a good PSU is always a good move, try using a single monitor as a test to see if VRAM is the problem.
You may want to get a video card with more memory. When I got a GTX 1070 with 8GB VRAM, the crashes stopped happening.

Your mileage may vary.

Only way to find out would be to start swapping parts to narrow it down. Sounds like psu is choking

Hmmm . . .
IDK but maybe you can try to make and underclocking profile using MSI Afterburner?
I never had much luck with overclocking GPU's. It would always overheat and go back to normal.
At best you only gain a few percent better by overclocking a GPU.
Underclocking will only lose a few percent, but that's better than being unstable.

Try going into settings and check 'Unlock Voltage Control' and 'Unlock Voltage Monitoring.'
Make a Profile with minimum Core Voltage and minimum Power Limit.
Then set that Profile to be used in 3D situations.

As I said, I am no expert at GPU O/C either.
But I do know that by lowering the power limit you are underclocking and there is no danger.

The key with Overclocking or Underclocking anything is
patience, writing things down and making small adjustments until you get it right.

Usually it gets to the point in my overclock where it works, but might crash a few times, then I back off one notch.
My CPU overclocked to 4.6 GHz. It crashed once and I put it at 4.5 GHz. It never crashed again.

Try moving the power limit to 90%, then 85%, 80%, 75%, etc. A little lower each time.
When you get too low a voltage the card will start to crash because the chips don't have enough power.
It's crashing now at 100%, so you have to find the lowest point where it crashes and settle for a stable voltage in the middle.
Save separate Profiles for each setting. But don't apply those Profiles yet, just save them.
Always leave Profile #1 unchanged as your 2D setting or fall back to stock setting.

Then in Afterburner settings go to profiles and assign the 3D profile to Profile #2, #3, #4, etc.
Stress Test the card by running a bunch of things at the same time.
MSI Kombuster + Photoshop + YouTube + a game + a CPU stress test. I use OCCT.
You are trying to make it crash, by making it go faster than any sane person would do.
If it works for a crazy person like me, it will work for you.

Once you get that working, you may also want to change your 2D Profile setting to one that you altered.
Imagine you could have 2D profile as 90% power limit and 3D profile as 85% power limit.
Usually when overclocking you go the other way 105% up to 110%.

It's almost impossible to destroy a card with one overclocking attempt.
Unless you are dumb and slide everything to the max on your first try.
It's not like they blowup, they usually lock-up and fail to boot or or it crashes all the time.
Then the GPU BIOS has to be reset to normal. I have never had to do that.
(Check your manual. Some cards have 2 BIOS. One to mess with and one as back up with an easy switch. Some have to be reset by shorting a jumper.)
Usually they only burn out or just wear out faster if you leave it at higher voltage than you should for a long time.

You are reducing voltage. You are underclocking.
It will wear out slower. Don't worry. You are fixing it. Not risking it.

As I said, I am no expert at GPU O/C either.
But I do know that by lowering the power limit you are underclocking and there is no danger.

The key with Overclocking or Underclocking anything is
patience, writing things down and making small adjustments until you get it right.

Usually it gets to the point in my overclock where it works, but might crash a few times, then I back off one notch.
My CPU overclocked to 4.6 GHz. It crashed once and I put it at 4.5 GHz. It never crashed again.

Try moving the power limit to 90%, then 85%, 80%, 75%, etc. A little lower each time.
When you get too low a voltage the card will start to crash because the chips don't have enough power.
It's crashing now at 100%, so you have to find the lowest point where it crashes and settle for a stable voltage in the middle.
Save separate Profiles for each setting. But don't apply those Profiles yet, just save them.
Always leave Profile #1 unchanged as your 2D setting or fall back to stock setting.

Then in Afterburner settings go to profiles and assign the 3D profile to Profile #2, #3, #4, etc.
Stress Test the card by running a bunch of things at the same time.
MSI Kombuster + Photoshop + YouTube + a game + a CPU stress test. I use OCCT.
You are trying to make it crash, by making it go faster than any sane person would do.
If it works for a crazy person like me, it will work for you.

Once you get that working, you may also want to change your 2D Profile setting to one that you altered.
Imagine you could have 2D profile as 90% power limit and 3D profile as 85% power limit.
Usually when overclocking you go the other way 105% up to 110%.

It's almost impossible to destroy a card with one overclocking attempt.
Unless you are dumb and slide everything to the max on your first try.
It's not like they blowup, they usually lock-up and fail to boot or or it crashes all the time.
Then the GPU BIOS has to be reset to normal. I have never had to do that.
(Check your manual. Some cards have 2 BIOS. One to mess with and one as back up with an easy switch. Some have to be reset by shorting a jumper.)
Usually they only burn out or just wear out faster if you leave it at higher voltage than you should for a long time.

You are reducing voltage. You are underclocking.
It will wear out slower. Don't worry. You are fixing it. Not risking it.

As I said, I am no expert at GPU O/C either.
But I do know that by lowering the power limit you are underclocking and there is no danger.

The key with Overclocking or Underclocking anything is
patience, writing things down and making small adjustments until you get it right.

Usually it gets to the point in my overclock where it works, but might crash a few times, then I back off one notch.
My CPU overclocked to 4.6 GHz. It crashed once and I put it at 4.5 GHz. It never crashed again.

Try moving the power limit to 90%, then 85%, 80%, 75%, etc. A little lower each time.
When you get too low a voltage the card will start to crash because the chips don't have enough power.
It's crashing now at 100%, so you have to find the lowest point where it crashes and settle for a stable voltage in the middle.
Save separate Profiles for each setting. But don't apply those Profiles yet, just save them.
Always leave Profile #1 unchanged as your 2D setting or fall back to stock setting.

Then in Afterburner settings go to profiles and assign the 3D profile to Profile #2, #3, #4, etc.
Stress Test the card by running a bunch of things at the same time.
MSI Kombuster + Photoshop + YouTube + a game + a CPU stress test. I use OCCT.
You are trying to make it crash, by making it go faster than any sane person would do.
If it works for a crazy person like me, it will work for you.

Once you get that working, you may also want to change your 2D Profile setting to one that you altered.
Imagine you could have 2D profile as 90% power limit and 3D profile as 85% power limit.
Usually when overclocking you go the other way 105% up to 110%.

It's almost impossible to destroy a card with one overclocking attempt.
Unless you are dumb and slide everything to the max on your first try.
It's not like they blowup, they usually lock-up and fail to boot or or it crashes all the time.
Then the GPU BIOS has to be reset to normal. I have never had to do that.
(Check your manual. Some cards have 2 BIOS. One to mess with and one as back up with an easy switch. Some have to be reset by shorting a jumper.)
Usually they only burn out or just wear out faster if you leave it at higher voltage than you should for a long time.

You are reducing voltage. You are underclocking.
It will wear out slower. Don't worry. You are fixing it. Not risking it.