Yeap my Asus software isn't very good, Realtemp showing 21c on 2 cores and 37c on the others while Asus PC Probe 2 is saying 13c
If those reading are constantly at those sort of differences , 16 degrees , i would check the mounting of your cooler.
Looks like it not secured evenly.
It might have just been using just the 2 cores when you took the reading, try putting the cpu under load to see if all the core temps even out a bit.