i just noticed today that one of my 18 week old chicks had a viably large bump right where her right wing meets her breast. i picked her up and started feeling the large bump. I noticed that when i pushed on it it sunk in and then expanded back out. She is still growing some feathers in this area. Also none of the other chickens have this on them. So is this something I should be concerned with or is it just the cartilage from all the new forming feathers? Any answers will be appreciated. Please help!!!!