I'm fairly new to keeping chickens and one of our about 12 week old chick seems to have much smaller wings than her sisters. She's a Black Sex Link and is the biggest out of the trio, and not by much. The others seem to have no trouble fluttering on to a stick a foot high but the BSL even struggles with the balancing on a stick barely off of the ground. Maybe it's just early clumsiness and the fact she isn't full grown?