In the beginning of winter our chickens started pecking each other and pecked one hen to death and injured 5 others. We had to separate the injured hens and put them in the shed. They all seem to be laying eggs and doing just fine but their feathers are not growing back and it's been a couple of months since they were pecked and they've healed since then. I also noticed that their behinds are all bare and bright red. Is it molting or something else? I looked at them in the dark with a flashlight for the signs of mites or lice but don't see anything. It's our first time raising chickens and I'm not sure what to do... The shed where the injured hens are is made of plastic and the rest are in a metal coop so I don't think they should have any mites since those usually live in the wood as far as I know but I might be mistaken. We separated the rooster from the hens a while back since it seemed like he was the reason for pecking so it's not the rooster damaging their skin. Has anyone had this problem before and knows what can cause feathers not to regrow after pecking and also why do hens lose their feathers on their behinds?