Need help finding medicine for sick chickens

[TwoCrows]

It mostly seems to happen at night when they're panting in the heat. I don't usually hear it during the day, even if they are hot. It's probably pretty dusty in there. It's a big barn, but it really needs to be cleaned out. I've been removing the excess dirt and debris to reduce the amount of dust in the air. Hopefully, that helps.

Yeah it sounds like an air quality issue, after cleaning it up you might install a vent fan in the roof to help move the heat out of the ceiling? During the day I run a fan pointed at the ceiling towards the vents to keep the warm air that gathers up there from building up. It definitely helps to cool things off at night. Leave any windows you have open at night too, just make sure they are covered in hardware cloth to keep night time marauders out. If it's really roasting at roosting time, leave a fan running to stir up the air. During the day I point fans directly on birds, but never at night. Stirring up the air at night will help them breathe better too.