How to remove stains and sagging fabric?

I bought this motorhome with a fear the roof leaked due to the stains on the roof and the sagging faric, but we replaced the roof vents, and there is no leaks. The stains almost appear to be older water stains. I used my steam cleaner on them, and funny but it helped the fabric to re attach itself, but did not remove the stains! Anyone have the answers to this delemia?