coughing or sneezing hens, what to do?

[LandRover82]

I had one Polish Black hen that started sneezing or coughing, hard to tell the difference. Now three or four have it.. what do i do??

 

[Eggcessive]

How old are your birds and where did they come from? Have you added any new birds to an existing flock? Most respiratory diseases come from a carrier, but MG can also be transmitted via hatching eggs. Do you see any bubbles or foam in the eyes of the sick birds? Is there any nasal drainage, swelling of the eyes, or crackly breathing? The link below gives symptoms of several common respiratory diseases, such as infectious bronchitis, infectious coryza, ILT, and mycoplasma gallisepticum (MG.)
https://edis.ifas.ufl.edu/publication/ps044