One of my peyote's is turning a little brownish. Is that bad? It's texture still feels the same when i touch it, so it doesn't seem to be rotting or drying out. I recently had to cut away some pieces of another one that where being affected by a sort of fungus (white sort of moisty dots). I think i may have had exposed them to too low temperatures because i have them in front of a window.

do you water, are they in artificial light?

No artificial light, they are standing in my windowsill. They get a bit of water about once every two months.

hmm, sounds like you are doing fine on the watering, and I assume there is no direct sunlight either. Just leave it alone, it will recover, or not. Some make it some don't. If the others don't show signs like this, I would not worry!