Testing would need to be done to confirm anything. You really didn’t post bad info. The vet links I read said that there can be a similar disease to coryza in quail, but it is a different bacterium. I am certainly not an expert of coryza or MG. Here is where I read that...
Does the face have a bad odor? Have you added any new birds or seen any respiratory disease in other fowl? Coryza is actually a disease of chickens, but quail can get a similar sinus infection from a different bacteria. MG or mycoplasma can look a little similar. You should get some antibiotics...