Last week we introduced a new 5 week old chick to our flock (of 2 other 5 week olds). Things seemed fine. This morning when we went out to feed them the new chick is missing a wing. Not bleeding freely, just red and sore looking. She's eating and drinking. We have not observed pecking, in fact, the three of them sleep together at night. But this is our first chicken attempt and we don't know what to do. Medical treatments? Separate them? Help!