Ambient temperature 18-22C
I tried the heatsink that came with the processor and it was giving similar temperatures +5 degrees to each core, if all my temperatures were running at the core 3 and 4 temps I'd be happy, it's core 1 and 2 temps that really bother me.
I think those cores only use two temp sensors. One is for cores 0 & 1, the other for 1 & 2.
If I were to hazard a guess, it would be that the sensor between 0 & 1 is reading incorrectly.
Intel does have a prog that will test the sensors, but I've lost it, so hopefully someone else can pass it along.
Since you are 50c away from critical temps, dont worry too much about it.