I have two birds with roughly the same symptoms/progression. A little over a month ago when I was concerned about a possible outbreak, I quarantined two chickens, Chubs and an unnamed Australorp. Both had an issue where their whole bodies seemed to inflate when they breathed. Neither had any coughing, sneezing, odd noises, runny noses/eyes or any other symptoms typical of respiratory infections other than that occasionally the Aussie would occasionally gasp for air, usually after she'd eaten. I had a different chicken with the same symptoms die suddenly and had her taken to a state lab to be necropsied. The results were inconclusive. They did not find any infections or odd signs other than that there was some swelling in her brain and changes to her heart structure. The hen that passed was nine years old. After I got the necropsy back and they did not believe it was an infection, I allowed Chubs/the aussie back into the flock. About 3 weeks had passed since I penned them. I started them both on Baytril, .6mL once a day. It's helped some with Chubs, but the aussie still has symptoms. She also lies down a lot and seems disinterested. She isn't nonreactive or really 'listless.' One big thing was that one day after she had eaten some corn, she coughed up a huge wad of semi-opaque white phlegm along with a few corn kernels. I really have no clue what is going on, especially because A) the necropsy on the other bird said it wasn't an infection B) she's been on antibiotics for over a week and C) she hasn't really gotten better or worse. Her condition is pretty much the same. Does anyone have any clue as to what is going on?