FWIW & IMHO:
This might be a little pricey, but I think that the results would be commesurable with the cost.
Dis mount rims
Take the rims to your friendly polisher/plating shop and have them professionally polished. Sounds like the "elements" have gone deeper that can be removed by hand polishing. You might want to try and sand by hand with very fine "wet or dry' sandpaper locally in a very small area and then re-polish by hand. Gonna be a real bitch, though.