I have a mixed flock of birds 16 weeks to a year and a half in age. They started sneezing when the cold weather came around but only once in awhile and different birds each time I would hear it. I would have to stand out there for awhile to hear one. No mucus or snot anywhere, No swollen or watery eyes. Then my young 16 week old rooster sneezed and a few hours later went lethargic and died in a time period of 6 hours. I took him down to be autopsied in Reynoldsburg at the Ohio Department of Ag and the only thing they could tell me was he had pneumonia and he didn't have a disease, virus and when the cultures came back they said he didn't have MG. So my vet had me give the flock tetracycline in their water for 7 days. They still sneezed, lots of pale combs but all eating and moving like normal. Then after antibiotic I started them on probiotics to get those good bacteria back in their systems and a day later lost one of my Easter Eggers (Emily). I just found her dead on the coop floor when I went to let them out in the morning. I also had one of my SLW go lethargic so I brought her in and took her to the vet while she was still alive. He felt since she had diarrhea we needed to give her bactrim twice a day to save her. So I kept her in the house gave her bactrim orally twice a day and she got better. So after another Easter Egger died on my coop floor two days later the vet prescribed bactrim for flock..which I gave to 18 birds every day twice a day orally. (Not fun) So now i still have sneezing some pale combs and one of my Delawares is laying down a lot and having a really hard time breathing. I dump waterers out every night they get fresh water in mornings with vitamins or ACV. I bring in their feeders every night. Their area is clean and they are wormed. My vet checked a lot of poop and verified no worms. I am at a loss as to what to do next.