Fabric could indeed be fine
FWIW dept:
When we bought our boat, one of the first things we had to tackle was moldy and mildewed cushions. The covers were in good shape physically, but the foam was both flat and full of black mold.
We tried washing the foam, but it was a waste of time for multiple reasons.
So we took off the covers and laundered them in a combination of mild soap, a little bleach, and warm water. Three times. That got rid of 98% of the smell and they were still intact and looked great. (There was only one that was visibly worn enough to need outright replacement, and that was the nav seat, and it was replaced. Remaining odor was ousted with some ozinator treatments.
With new hi-density foam (2.6) and then having that wrapped in dacron fluffy material, the re-stuffing was a great success. That was ten years ago and they still sit and sleep without bottoming out.
Buttons on the settee seat backs were re-tufted, of course, also.
New zipper pulls were fitted to replace the originals -- most of them transmorgified into lumps of oxidized aluminum...
Loren
1988 Olson 34