How do I remove stains from DMC floss?

by Rebeca
(Florida)

I just finished a cross stitch project using DMC floss.

I washed the finished work with mild soap and water but one of the brown floss stained part of my work. I found the stains when the project had been dried, tried again to soak it in water and clean it with soap but the stains are still there. Is there anyway I can remove these stains.

Help!!! this is a nice work and I spent many hours on it. I want to frame it but, if possible without the stains. Thanks!!!