I need treatment advice for a respiratory problem in my flock of chickens. I have a flock of 22 hens and 4 are sick with some type of respiratory issue. It started with one hen back in July and I just recently noticed similar symptoms in three others. The main symptom they have is a congested sound in their breathing. I can hear it when I hold them to my ear. One sneezes ocassionally without any nasal discharge. I don't know what I am dealing with or how to best treat it. If it is a respiratory disease would it take months for it to go through the flock? Could it be a fungal infection? Any advice on what I am dealing with or treatments would be appreciated. Thanks!