I have 1500 km on my new 08 wing and my wheels seem to be starting to discolor already. By that, I mean there are white streaks through them that I cannot get off. I bought "Bluemagic" metal polish cream and spent an hour cleaning them and although they did clean a lot of the road dirt off them, they still have these annoying streaks through them. Is this natural or is there something else I can do?