5 to 5 1/2 week old BO chick seems to not want to eat food or drink, but will eat grit and other stuff outside. she seems small to me, not sure on weight, but she was the smallest of all the BOs in the bunch in the feed store when we got her(my daughter picked THAT ONE!) she is almost fully feathered except her head. she is growing, just not at the speed i thought she would compared to my other chicks, although she is the only BO. the last few days, maybe 2 or so, she will open and close her mouth and slightly stretch her neck. today she was sneezing a bit. no discharge from anywhere, eyes look good, normal poo, typical energy. all the other birds seem fine. i tried to check for lice and mites, but that didn't go over very well. they are all on manno pro medicated chick starter. anything to worry about or do i have a runt that may be being bullied away from food and water? and i checked for her crop, and i can't feel it. it's 4pm. shouldn't it be full by now?