Syble -- I'm so glad to hear your others are recovering.
I put vinegar in the water at times for all of them. It can't hurt. Generally, I put 2 to 4 tablespoons in a gallon, and I use raw organic vinegar so it has live microbes in it. I don't do it all the time, maybe once every other week. I don't know if it really does anything, but as I said, it can't hurt.
I haven't tried feeding them cayenne yet per se. Last year, at the end of the season when I was doing garden cleanup, I threw some old pepper plants with some hot peppers still attached in to my chickens and turkeys, and they cleaned up everything but the woody stems. But they were mild types of hot peppers, anchos and anaheims, not the really hot stuff.