I looked at the photos and I didn’t see evidence of mites or lice. Look at the bases of the feathers for some tiny fuzzy dots. Then look for tiny little bugs on the skin near the vent. They are VERY small;can be red. I had this on my chickens, used 2 drops of frontline on their neck and 2 drops below the vent. I also cleaned out the coop and scrubbed the walls, roosts and nesting boxes with Elector PSP. No problems since I did all of that. I have a lot of wild birds flying in and out of the coop looking for food (mostly sparrows)and theymight be a source of mites and lice. Everyone is clear now. Good luck with your flock