I have 2 blue cochins, both 2 weeks olds, and 1 is about 75% bigger than the other. The smaller of the two is not much bigger than my 1 week old brahma. She also feels kind've bony- but maybe that's my imagination. Other than growing slowly, she seems to be fine. She's alert and active, no loud cheeping, no pasting up. She does spend more time under the lamp than my other chicks, I think. Maybe because she does not have as much fat or mass. Oh, and she does not seem to be getting her feathers as fast as the others. What gives? I'm not sure if I should be worried about her or not.