I bought a new hen about 3 months ago, separated them for about 2-3 weeks to make sure she was fine before i put her in the coop with my other babies. About 2 days after i introduced the new hen, following the 2-3 separation, she started sneezing, and I did not really think anything about it as she was healthy and so was my flock. The sneezing slowed down and with in 2 weeks of her being there with the flock all my chickens started sneezing. No coughing or runny nose or anything, just sneezing. This happened for about 2 weeks, just only sneezing but late last week early this week, they started coughing a bit so I called the vet and she told me to get Sulmet and treat them for 5 days. Today is the 4th day they are on the antibiotic and all seem well yesterday. Hardly no sneezing and no coughing at all. I got up this morning and all of them are sneezing like crazy, and my Roo is coughing and has a buggery nose. I moved him out of the coop. They are all eating and have lots of energy and drinking normal. No runny poops or anything.I put Vet Rx on there nostrils this morning and under their wings ( boy they did not like that at all ), Any idea's on what it might be. They also quit laying eggs about 5 days ago. None are egg bound and they have all their feathers, not molting yet.