I would get that hard stuff off. It could be clusters of mite eggs then treat her to more dusting. I would spray her coop because if she is in with other birds, there is a chance they all have some mites.Yeah I hate mites, they make the chickens suffer so badly. I got permethrin dust, would that do the same job or would spray be better? I've noticed little hard mite stuff on the feathers under their chins, but it's too dark right now to take a picture and they are too fidgety for bedtime.