I have 1 week old Cornish Rock chicks. I picked them up today (moving them around) and noticed that most of them have chest/belly areas that are pretty bare of feathers. Have the feathers rubbed off? They do spend alot of time on their bellies, resting, is there a problem I should be aware of? They do get up and eat, drink, etc. They don't seem cold (they don't huddle under the lamp or all bunched together).