Just brought some diamond cut wheels and 1 of them as some marks, not scrathes just looks like dirt but tried metal polish and metal t-cut, its now shiny but still look dirty!

wheels are mint and really want to get them all shiny and new looking!

Thought maybe if i was to take them to some one with a metal polishing machine i could get them done, but would i need whole wheel doing or could i get just the dirty bits done??

any help greatfull!