There is no cure for respiratory diseases, only treatments. Sulfa drugs including sulmet treat coryza. The problem is that since the sulmet is mixed in water, sick birds wont drink, and if they do it's usually not enough to be effective. Additionally there's a possibility that mycoplasma gallisepticum might be a player as well. Coryza sick birds exude a foul odor around the head area. If there's no foul odor, you could be dealing with a severe strain of mycoplasma gallisepticum instead of coryza. Sulmet is ineffective against MG.
If they are laying eggs, are there any weird or wrinkled looking eggs?
I've gotten two leather eggs, but that's it... Oh, and one double yolker!
Ok, In 4 months I've only gotten two odd eggs, they have swollen heads, and gasp when they eat dry feed. No sneezing, coughing or runny nose, only one is swollen badly in the sinuses. The rest is just a slight swelling around the eyes. I won't be able to go get a necropsy for some time, but is there anything that I ca give to alleviate symptoms? No bad smell
