Then if there's no ammonia smell, you may be dealing with a respiratory illness. Hard to know.The coop is 8x16 and has 3 windows and ventilation at the roof overhang. I’m not a builder There is no smell of ammonia. And these birds are not new but we did add 8 about 3 months ago
If you can get injectable Tylan50 then you can direct dose the symptomatic birds orally 3 times a day at a rate of 0.25ml per pound of weight for 5 day. This will ensure they are getting the medication instead of relying on them to drink mixed Tylosin powder.