Shortly after delivery, I discovered thousands of iron spots on my M3 SR+, mostly on the trunk lid and the partly horizontal parts of the rear quarter panels. Locally, I could find only Meguiar’s Iron Removing Spray Clay. It worked reasonably well. Attached photos show the stains and the reaction on my first treatment. It took several treatments and light action with a wet wash mitt to get most of it. I bought some Iron X to use the next time I wash. A couple years ago I had a similar issue with a white Toyota. I hired a detailer who used a similar product.