We have a fabric ceiling overhead also. Last year we had a small leak and it stained the ceiling in a 4"x3" area. I mixed a SMALL amount of bleach (1-2 tablespoons) with a spray bottle of water and sprayed down the stain. I let it sit a few minutes and then blotted it with a paper towel. Repeated 2-3 times over a few days. You cannot find the stain now unless you look for it.
Try a small area first and see if it works.
Burns & Diane
2005 Winnebago Aspect 26A/2012 Subaru Impreza toad
Illinois! - Where the politicians make the license plates......