I have one Cochin and one Welsumer. Both are about 30 weeks old and seem healthy. They're each laying regularly and have pretty roomy living conditions for two chickens.. Today, when I got home, the feathers on the back of the Cochin's head and down the back of her neck were gone. She still seems healthy but sure looks funny. I guess it's some kind of skin condition or maybe the Welsumer's doing it. Any ideas?