I have several chicks in the brooder right now, and one of my RIR's seems to be developing feathers much slower than the others. It's around the same size as the other chicks, but while the other RIR's have two or three rows of wing feathers and tail feathers poking through, this little gal (or so I'm hoping ) has only one row of feathers, no tail feathers to speak of, and still has a lot of her chick fuzz. What could cause this? She seems happy and healthy. They are all just over a week old, on medicated chick starter.