We just experienced/are experiencing our flock having MG, which is one of the respiratory diseases you'll find above. All of the chickens seemed to have different symptoms. Some just sneezed, the worst two had gurgling/snotty noses, and all had swollen eyes. One had swollen watery. bubbly eyes. We gave them Tylan 50 orally, 1cc for a 5lb chicken 3x a day is what we were told, and I also gave 1cc of coilloidal silver orally as well. I put Vetrx on their nostrils 2x a day. It's been about a week and they are looking so much better. but I did have to give water manually to the two worst presenting chickens and I kinda force fed them too (just put pellets in their mouth, they would then eat). From my understanding the respiratory disease will always stay with them. Many people seem to choose to cull the entire flock. We don't plan to sell our birds, because they could infect other flocks and that would be a terrible thing to do. If your birds have MG, they will pass that on as they lay so if you want chicks from them, please don't sell them because they will infect other flocks.