My cornish cross pullets are about 4 weeks old and I have been noticing that all of them have a swollen growth around the base of their necks. It looks like a big soft golf ball sitting on one side of the neck (on top of the wishbone) and is on every one of them. Anyone know what that is? It is not painful to them because when I handle them to investigate they don't complain and I can even touch it. None of the other twenty pullets and roos have them, I just wanted to be sure that they aren't sick or something.