At one point 5 out of our 6 hens seemed to get bare bums all at once. We worked out it was one of them pecking the others bums, and we gave her and one other to my in-laws. Those two are now living in the lap of luxury in acres of space and the bum pecking has stopped. Now we have just 4 hens and 3 of them have grown their feathers back. The 4th hasn't though and her bum looks a bit pinker than the others did. It's not raw or sore looking, just dark pink. She is the biggest and stupidest of them and seems also to be moulting at the moment when none of the others are. Her neck feathers are getting thinner and there are feathers in the coop. Will she grown them back or do we need to take her to a vet?