I think it might be Coryza. This is kinda serious, and spreads easily. Check out this link, and see if your birds have any other symptoms. If so, there are medicines you can give them, but some might die and the ones that dont will always be a carrier of the disease.
If its not this, there could be some chemicals or somthing in the air they could be allergic to. I had a turkey who's face swelled up after my neighbor sprayed insecticide on her bushes, so thats a possibility as well. Good luck.