I have a sick chicken and hope you can help me identify the problem and also treat it. She is a young Rhode Island Red, almost 4 months old. For the last couple of months she has had a large water balloon like area on her breast. It didn't seem to bother her, she ate and drank just fine. She also scratches in the grass/dirt and seems to feel ok. But, last week, she started coughing and sounding crackly when she breaths. She pants very hard, which they all do in the heat, but it seems to bother her more. This morning, she threw up a yellowish liquid, twice. She is still eating and drinking as usual, and not sounding so crackly, but the large water balloon area is still there. I have been putting terramyacin in their drinking water since Friday evening. What are your suggestions? Thank you,