Pre-coated parts are often not done with top quality products and I have had a pair of ramhorn knock offs do the same. This time I sent my own parts to Jet-Hot in hopes of a more durable finish. They offer a lifetime waranty and claim in videos that they are often recoating parts just like yours. They did mine with "silver polish" and Ive got a few good drives on them now and they still look great.
https://get.jet-hot.com/?utm_source=...RoCr6IQAvD_BwE