Others will chime in on this since I do not use screened bottom boards. You say you use the screened bottom board, but to me it looks like your hives are sitting on solid wood for a hive stand, is this not defeating the purpose of the screened bottom board? Just thinking out loud here.
Different hives will work at diferent rates, I have a nuc that is killing me because they are so slow to build comb, and a hive beside of them (from a swarm caught on 4/29) is going like gang busters, have robbed out three frames of capped brood for other hives.
Good luck with them.
G3
after going back a looking at your pic I see the bottom of the hive stand is slotted. Are you having skunk problems? i see you have a fence charger on the front of your hives.