Best way to whiten sails?

Hey gang... some squirrels decided to chew through my sail box over the winter to camp out in there. As a result, my white sails have some reddish-brown stains I don't even want to know where from. I thought about cleaning them with a bleach-water solution, but I heard someone say bleach could be bad for the sails. Scrubbing with dish-soap and water helped a *little* bit, but the stains are still quite noticable. Ideas?

Thanks!

Jim

P.S... "Shoot the squirrels" is not what I'm looking for here.