I am new to the backyard chicken experience. However, I should've known better than to introduce a new chicken to my other girls without an incubation period. Live and learn. Long story short I put a hen I had just acquired from a breeder in the with my 3 other backyard hens. That evening when I went to close up the coop I noticed she was coughing and sneezing. Within about 3 to 4 days my other 3 hens had come down with it. They are between 1 and 2 years old. For a while they sort of went off their feed. It's been 4 weeks now and I have treated them with 2 different rounds of antibiotics. Two of the hens have recovered somewhat and the other 2 are still coughing and sneezing. I have a set of 11 8 week old chicks that I have separated into the front yard so they don't come in contact with the chickens. I would like to get them so that I can get everybody moved into the coop before winter hits. I just vaccinated all of the chicks for viral influenza on the off chance that might be it. Any ideas? Thanks in advance for your help.