I have eight chicks that I've had for about three to four weeks. So far everything has been fine, but lately I've noticed one of my Rhode Islands has a big crop. I didn't worry about it because my two Brahmas had big crops at one point, but they grew out of it eventually (they're a few days older than the Rhode Islands.) Just recently while she was eating the Rhode Island started to have mucus come out of her beak. It was foaming and some of the other chicks were pecking at it. I got her out of the cage, but she stopped pretty soon. My mom thinks she just sneezed, but I think she might be sick. What should I do?