same problem here...but i fixed it...
Pull out the washer res and remove all the fittings. where the tire rubs, heat it with a propane torch carefully. you want to get it soft, but not damage it. once its soft, push it in with something like a small block of wood and let it cool pushed it. you may need to push pretty hard. Keep repeteing this as needed. do just a bit at a time, so you dont damage it. Then put it back in and pull the inner fender back from the tire by drilling two small holes in the inner fender and looping a zip tie throught it and back to something secure.
It sounds a bit rough, but the tank is not seen behind the inner fender and the zip tie is black so it blends in. you have to get on you knees wit a flashlight to even see it.
I got about 1.5 - 2 inches of clearance out of it. You will need at least keys.
I have a similar setup (20x8 rims though) and have no rubbing on the washer res after a year like this. the res doesnt leak either.
Good luck!