I am new to raising chickens. I have a hen that has lost all her feathers on her back and is starting to lose them under her tail. She is a Bantam, approximately 1 year old. This condition has been gradually worsening over the last few months. She is one of three chickens, 2 hens and 1 rooster and the others are fine. I have limited her exposure to the rooster, as I have read he could be the cause, and have also clipped his nails. She is on a commercial layer feed and I supplement that with game bird feed, scratch, grit and an occassional handfull of dried cat food. All the chickens roam free during the day. What more can I do to help her? Is there something missing in her diet?