Ok, slow down. Tonight, after dark, go out to your coop with a flashlight. Take a look at the roost. Stay a minute or two. Watch carefully. If you have mites, you will likely see them moving on the roost, tiny specks, moving. Another member has advised to take a piece of white paper or similar, and rub it along the roost (also at night preferably) and if you get red/blood smears on the paper, you probably have mites. Take pictures if you can. Update us with your findings. No sense in treating for mites if that's not even what you are fighting. Unfortunately DE is not going to kill mites if you have an infestation, but there are other products that can. My coop had lots of mites, but I never actually saw them on the chickens. Other places to look would be corners, where the roost attaches to the wall, and nest boxes.