I have some young bantams that are in my "grow up pen". Their eyes are closed and puffy. They act normal and happy but annoyed. Not all of them are like this. My silkies eyes are both closed. And a couple have one closed and the other open. But one doesn't have eye problems but has rough breathing. Here is some pics.
It sounds like your chickens have/are gradually developing a respiratory disease. I would get some oxytetracycline to put in their water. Oxytetracycline can usually be found at a livestock supply store, and is sold under names like Tetroxy HCA-280, Duramycin, Terramycin, etc. The dosage varies with each product, but they are basically the same thing.
I agree, this is a possiblity. Is it possible that their coop is dusty, or has a high level of ammonia? That can also cause these symptoms. If they are acting normal otherwise, that may be the problem instead.
Thank you for replying! I have them in a pen that I can move around. So every week I move them on fresh ground. This makes me mad... I had some of these guys for sale ready for new homes. But when I noticed this I didn't sell them.