https://www.metzerfarms.com/poultry-labs.htmlWhat state are you in? Most state vet labs will do a necropsy and testing on chickens that die, if the body is kept cold, not frozen. They will identify the certain respiratory disease present. Both MG and infectious coryza are respiratory diseases that cause swollen eyelids and serious respiratory symptoms. Did you notice a bad odor from the beak or face from the sick birds? Tylosin can be used to treat MG, while coryza is better treated with sulfadimethoxine or SMZ TMP (bactrim.) Here is where to find your state vet lab for a necropsy if you lose another.