Hi we have a plymouth rock that has all her back bottom of vent feathers all gone and seems like the skin is gone also. She is 11 months old. I was told that it looks like we are looking at her egg sack because the skin is missing. We cleaned her and sprayed blue kote and have also moved her into a separate area because the other chickens were pecing at the wound. The wound feels dry and crusty. Any help as to what it could be and what to do is appreciated. We checkec for mites and she is clean.