@Phillyfan I don't think Cartier does it, I'd have to take it to my local jeweler. Cartier uses palladium white gold which sustains the whiteness without yellowing, but I'd just like it to be more shiny. I keep thinking I should have gone for the rose gold and diamond instead of wg diamond, but I wanted it to match my rings which are 18kt wg and platinum.
It's not expensive at all to rhodium plate. I swear it was shinier when I first got it. Now it looks like this: