No mites, No lice, No rooster, no fighting...so what could be going on with her? She is the only one with missing feathers. It is on her lower back before her tail. She is only 25 weeks old and has been laying for 8 weeks now. We have new clean coop and run.She is fed purina layena, scratch and scraps. Lots of excercise room and fresh sunshine. Able to go in coop whenever she wants to. Fresh water always. Any ideas?