If it truly is oxidisation under the clear-coat, the only way to fix that will be to strip it back & refinish the metal of the rim surface before applying more clear-coat. Some have tried doing that in spots with very fine wet & dry sandpaper or even steel wool before re-spraying with a rattle-can clear, but I don't think the spot fixes ever really look all that good - the 'repaired' spots tend to stand out like dogs balls! :shocked:
So, at least IMO, the best way to remedy those spots will be to strip & refinish the entire rim, but that can be expensive. :sour:
Or of course, you could buy a couple of brand new rims, altho I'd suggest it might be worth trying an after-market supplier & product - this is one instance where I reckon the A/mkt rims will almost certainly be a better finished & very likely better all round product! (Pun intended!

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Good Luck! :thumbup: