You've got it, that middle card can't breathe. If the different cards have different types of blowers, might be worth switching up the order.
They are all duplicate cards, 3x sapphire 5830's. Such a waste if I can get these 3 working. Im doing fine 2x on each machine for 2 machines, but this 3rd rig wont work, 83+ now, totally need to figure something out. How the hell are people shoving 3-4 cards in a case?