How to make canvas shoes white again?

Hi, I have 6 year old Nike Dunks Melvin, and these are really expensive shoes. They go more than $190 now a days since they're limited edition and such. But, I have some mud spots on them, and it seems like it's really in the canvas material, and I'm wondering how I can get it to turn white again? I've tried Tide To Go, scrubbing them with detergent+bleach, baking soda, and vinegar. Is there any way I can get them clean again? I don't want to put them in the washing machine because it could really mess up the glue in the shoe and such like that. Any good products out there? Thanks