8 month old hen suddenly struggling to breathe she does not show any other symptoms such as sneezing or coughing and I do not see any discharge. I had a rooster die a few months ago with what I believed was wet pox and a pullet died about the same time as the rooster that started like this hen and was dead in 3 days after the first signs of struggling to breathe she also showed no other symptoms but the gasping.I didn't necropsy either of them and I have not had any other sick chickens since then out of about 60 birds.I have been reading the symptoms of the common diseases that cause these symptoms but she doesn't exhibit some of the other symptoms of MG or wet pox, etc.