I've got about 60 birds. The other day I got a really nice healthy batch of barred rock pullets and an old rir hen. The rir hen developed respiratory discharge and had to be put in quarantine. Now she's dead but my other bird are getting the same crap. Nasal discharge and eyes are swelling shut. I treated their water with sumlet and put them all on medicated feed. I've been putting the birds showing symptoms in quarantine. Thinking about giving LA 200 orally as a last ditch effort. Can anyone direct me to a diagnosis or a cure please?!?!?