I have 5 chickens . ONE hen has this bump on her tail end. It looked as if it was molting . I picked her up to take the picture . She felt dry along with all the feathers and dandruff like . I thought it could be mites, but did not see anything moving. The other chickens are all ok. the coop is new. She is eating laying and all things chicken. Let me know if anyone has an idea as to what this can be.