These 3 cards are identical Gigabyte HD7850's 2GB. Why is one 7850 at 78 degrees, but other two at 54 and 57? Each and are pumping out 362kh each.

Identified them by stopping the fans with my hand to see which one heats up or cools down. Tried re-seating the heatsink on the hot card and putting some better paste. Can't figure out why one of my GPU runs 20 degrees C hotter than the other two. All are hanging freely in the air and have decent airflow.

I am using this command...
cgminer -o http://coinotron.com:3334 -u **** -p **** --scrypt --gpu-fan 0-100 --gpu-engine 1050 --gpu-memclock 900 --intensity 12 --thread-concurrency 13632   --gpu-threads 2

GPU-Z shows all 3 cards all running fans at 100%. Only strange thing is one of the cards is showing a higher VDDC. But this is not the hot card! Any ideas?