I have a 8-10 week old lavender Orpington chick. She has straggly feathers on her wings and head/neck/chest but her back/hips/butt are completely bald! The others her age have all their feathers. Why doesn't she? She eats and drinks fine. We give her medicated chick crumble, lettuce, kale, cheese, chick grit etc. her poo is normal. I don't believe it's from plucking, because there is NO skin irritation at all! Anyone have a guess?