I've have mixed group of 11 birds that are 1 yr old. All of the birds grew a downy patch of feathers on their backs near tail feathers early in the winter (mild winter this year). Now all those feathers are falling out. Only one chick has grown new feathers, all the rest have bald patches with no sign of new feathers. They are not pecking each other and there are no signs of mites or lice. All are laying, as I get plenty eggs everyday. Any ideas of what's going on? I'd really like to clear this up!