I have about 35 chickens that are of many different breeds. I noticed a few sneezing over two weeks ago so I put them on duramycin10 for two weeks and the Saturday before last was the last day of the two week cycle. I've noticed since then that, although not as much, a few of my chickens are still sneezing, no discharge from the eyes or nose of any of my chickens, they are all active and seemingly healthy other than the sneezing. I never noticed all of them sneezing, just about 5 or 7 at the most, now it is maybe 2 or 3 of them that are still sneezing and I am wondering what could be the cause. Also, one two year old hen lost nearly half of her feathers in a matter of two or three days after starting the duramycin. And one hen and a pullet died rather suddenly the week before the duramycin was started and before any sneezing was noticed. I've also notice round worms in their stool and will begin treatment when I can, could this at all be linked to their sneezing? This is the first time I've had any sickness in my flock and the first time I've noticed roundworms as well. I also had a change of feed around the time the sneezing began, it was the same brand but a different type, could they be having an allergic reaction to the feed? I'd like to re-home about seven roosters from this years batch of chicks but I can't do so until I know the cause of the sneezing. Culling my flock is not an option as they are all pets used for the sole purpose of egg production. Any advice or knowledge on this issue will be greatly appreciated. I did not notice any sneezing today and egg production has doubled since I stopped the duramycin a week ago. I am thinking they are getting better, but my main concern now is what do I do with the seven or so roosters that I need to re-home? And is there any way to know for sure if my chickens are now carriers of an upper respiratory disease without a necropsy or an expensive vets visit?