Rooster and some hens have red bald butts and legs

[Birdchicken]

I don't think it's mites because I haven't seen any like when they have had them in the past but the hens have bald butts and legs and the rooster has it but it is very red. Any ideas what it is and how to treat for whatever it is?

 

[nuthatched]

Somebody is picking them, this is often caused by pests, imbalanced diet, small quarters for the number of birds, boredom, etc