Your core 0 is much higher than the others as program is single threaded.
While the tjmax is 100 c I think you will find that most users would recommend using a better HSF if temp is at or above 70 C (Stock HSF = poor - being polite).
My room temp is approx 79 F - My E6400 does not go above 60 with prime 95.
My I5-750 is also below 60 C (prime 95). I do not even install INTELs HSF, when I build a system I automatically order a 3rd party HSF.
I'm not a gamer, so you may be correct. But if it is using more than core zero, then he has a HSF problem. Either the HS is not properly seated (Common with intel push pins) or the paste is not contacting properly. He could run Prime 95 to verify. If the same temps are noted then the OP should check/reseat HSF. Normal diff I've seen in posts are less than 6 C from core to core while running Prime 95. Mine vary about 2 C for both E6400 (OC 3.2 GHz) and for my I5-750 (OCed to 3.8, currently runing at 3.2)
Run Prime 95. This will:
(1) test CPU
(2) Test memory
(3) Check how hot, and distribution, Your CPU will get.
(4) Also usefull to check Voltages at idle, and under Load. Furmark, a good program for checking GPU, Is better for checking +12 V stability.
The temps you listed (54->52) are acceptable, I'm not sure what "CPU" load the "... sands) places on cpu. Repeat, use prime 95 a Free download.
If Temps are @ or above 70 C. I highly recommend replacing the stock cooler. Myself - I keep my CPUs under 65 C at full load.
The higher the temps, the shorter the lifespan of a CPU and will vary with individual CPUs - The only question is how much and is it excepable. It may only be, instead of 10 yrs lasting 8 Years - But then again it may be 3 yrs instead of 5 years.
There are many posts that support the statement that the intel stock HSF is a poor choice. Myself, I normally buy a HSF with a backing plate - Hate the dang Push-pins!!