I’ve noticed two of my over a year old coturnix quail hens are balding on their backs. They are in a cage with two other girls which are younger than them and they aren’t balding. I checked for mites but I didn’t see any bites, eggs, or any bugs. I’m thinking it is from their age because they’re over a year old and their younger roommates aren’t balding. There are no Roos in the cage all are laying eggs daily. The younger ones have never bullied them or mounted on them or anything. Is this from age or something else?