I have 3 Easter eggers that are all fluffy on their butts like they just have their down feathers and one has scabs are her. They are 7 months old. I did just lose a 9 month old a few weeks ago. She lost all her feathers on her butt. I have been giving them feather fixer food and I have dusted them and the coop several times with DE insect dust. I don't see any bugs on them. Any Ideas?