she was damaged by overmating, but she's been with us for 4-5 months... shouldn't it have grown back? and why is it so red? she's been dusted for mites. maybe there was a slight improvement, but not sure. thoughts?
is she pulling out her own feathers maybe?
The others may be attracted by the redness and pulling the feathers, or the area could be sunburned. These areas may not grow back until the next molt.