I had a broody who hatched 3 chicks on March, 25th. Now that they are 9 weeks old I realized that they are ALL rosters, and one of them has missing feathers on his neck/chest. Only one of them has this problem (the other 2 are completely feathered out). The skin is red and bumpy and there are little stubs of feathers in that area. It doesn't seem like he's being picked on, do you have any idea what it is?