Thank you all for the responses on my rooster. There have been so many posts since then that I'm not going to try to go back and quote.
I don't have Denagard and looks like the only place to get it is mail order, so I may pick some up for the next time I need it.
I do have Oxine and I think we have a cool mist vaporizer, so I'll look into getting that set up for a while when I put him back in the coop. I think it would benefit all the birds in there. My other birds in the same coop (all sectioned off, but same airspace) don't seem to have any symptoms, although sometimes I think my blue Orp roo has it, but turns out he is just growling at me!
I do use ACV in the water when I fill them, not sure if DH or DS put it in every time when they fill them though, and they do the filling most of the time.
Mr. Freeze, my roo, is doing much, much better today. I have given him the Vet Rx 3 times now and sprayed some colloidal silver on his face/nostrils and in his mouth last night. He is still a little raspy, but much improved. I am hopeful that he will be back out in the coop again soon.