One of our chickens has a loose sack of skin on the front of it about the size of a tennis ball. The sack is slightly offset to it's right side and if I press on it, it feels like it has sand/grit in it. All of the other chickens are solid in this area. I wouldn't even have noticed but it's not symmetrical. The chicken is either a Dominique or a Barred Plymoth Rock, not sure. It is about 9 weeks old. The chicken seems normal. Eating, moving, and sleeping fine. Is this something to worry about or is is something about this breed that I don't know about. Maybe it's some kind of dewlap?