Hi everyone! I've been treating the henhouse and 2 hens out of 14 birds for mites/lice/something...doing this because they have lost feathers on their back in front of their tail feathers, and had some crusty looking fluff around their vent. I've been regularly dusting them and others (who have no signs or symptoms) for about 2 months now (poultry dust), and have DE well-mixed in their bedding, sprinkled on their roost poles, and in their nesting boxes. These two don't seem to be regrowing their feathers though. There also seems to be some feather loss from them and/or others in the nesting boxes when they lay...soft fluffy feathers. Anyhow, I have crept in at night, searched with a flashlight, held birds upside down, inspected cracks and crevices, under wings, around vent areas, etc., and can't really find anything that might be bugging them or others. Any ideas on what might be going on and whether this is going in the right direction or not? THANKS!