Mine has a tiny bit of rust on the top of the arch (not down as low as yours) going to mask flatten back and use red oxid primer and try to blend on the angle Current stable:
2006 BMW M6
2007 4.2 V8 S/C FF
Gone:
2002 4.4 V8 FF

I think the cars that get used heavily in the winter and never cleaned properly rot from early on in their lives...

Dunking boats in the sea is another good rot starter! And lets not even get started on our friends in Scotttttland with their weather and salt etc etc