Soooo I went to check on the chickens this morning and under and around the roost and in coop corners there are little piles of brown dust which are actually all dead mites that came out of the cracks last night! Eeeewwwww! I'm glad they are now dead but I feel so bad for the girls. It must have been millions upon millions of mites I've killed and removed from the coop over the weekend. I have no idea how long the problem has been going on and I feel terrible I didn't catch it sooner.