Slow internet on only one computer?!

[Tom Langley-Ballinger]

After browsing the web for any possible answer and trying so many different options to solve this, nothing has happened.
I know that it is nothing to do with my router/modem as various devices around the house are connected over WiFi and Lan and all pull around 36mb/s.
I have tested my computer using speedtest by ookla. I also tested while no other devices were connected.
I have scanned my device for malware using Sophos and Malwarebytes and no threats were returned.
My computer is connected to my router using a powerline adapter which has been perfectly fine and has previously pulled up to 38mb/s.
My computer:
Runs windows 10 (fully updated)
Uses a powerline adapter
Has A Killer Ethernet Adapter as well as an Intel Ethernet Adapter (this is the one I am currently using)
I can't think of anything else you need to know but any questions I will try and answer ASAP.
If anyone has any ideas any help will be much appreciated.
Perhaps I could use the Window's 'Fresh Start' option but I will see what you all say first.
Thank you!

 

[wpgwpg]

Have you checked Device Manager to be sure you don't have an incorrect driver? Have you checked Task Manager to see if something is inordinately busy? I recently had performance problems on my laptop that turned out to be a Superfetch problem. I ended up disabling Superfetch and the problem went away. YMMV.

 

[Tom Langley-Ballinger]

I have checked Device manager and the only two Network Adapters on there are the ones I mentioned - The Intel one and The Killer one. I've updated both drivers to the most recent windows can find.
On task manager the network section is being used almost always at 0% but does go up to around 5% but clearly there is not a program hogging the bandwidth.
Not really sure what else to do but thank you for your ideas.