I have a mixed batch of chickens and one rooster. I have a couple of Americana's both are fairly shy and non-aggressive with the other chickens. I've had one that I know has been laying eggs that will occasionally get a fairly large swelling in her breast area. She goes off her grain and just acts really sick. I went out the other day and I thought she was on her last leg. I picked her up and felt the swelling and sort of massaged it. The next day it was a little less and today it is gone completely. I looked up whats in there internally and its the craw area. I wonder, can they get an impaction of grain in there? I think I might have worked it free if they can. I've had chickens for about 10 years and have never come across this before. Is there something she isn't getting that is causing this? They get scratch every day and free access to oyster shell, plus regular layer mix.