Hi, I have a mixed batch of 24 chicks. They'll be 3 weeks old tomorrow (happy birthday, girls!)and, except for the four Barred Rocks, all have complete wing feathering, most of their breast feathers, and a few are starting to look pin-headed. The Barred Rocks, however, have little stubby wing feathers and are still fluffy everywhere else. They are sturdy, healthy and active, eating, drinking and pooping with the best of them. Is it normal for this breed to develop so much more slowly than the others?