I have 10 young hens and 1 rooster, that I have raised since they were 1 day to 1 week old, living in a comfortable coop with a run . Some of my flock have lost feathers around their tails and bottoms. I see no signs of lice or mites. They're not a year old yet and don't appear to be molting. Egg production has not slowed and attitudes have not changed. My chickens are contained where I can see them while in my kitchen, so I watch them very often. I've not seen any feather pulling. There is the common peck on the head, but no feather pulling. There are no feathers in their house or their run. I would expect there to be feathers laying around, no matter the cause for the loss. Does anyone have any ideas what is going on here??