It appears you have the coated alloy wheels, the kind that you don't have to polish regularly because they have a clear coat sprayed over the metal. When the lug nuts were tightened, the clear coat seal got cracked and corrosion worked underneath. I have the same problem on one wheel. I've thoght some about possible repair, but haven't done anything yet.
Unfortunately, the coating has to be removed to polish off the corrosion and then the seal coat re-applied. You could try to do it by hand, I guess. I'm assuming you don't have the heavy duty equipment to remove the wheel from the coach - it probably takes about 400-500 lb-ft of torque to loosen the nuts and those tires & wheels weight hundreds of lbs! So, Pull off the lug nut cover and protect the nut with masking tape or similar. Then try sanding/polishing around it as best you can. A Dremel or similar small rotary power tool is probably needed. Once cleaned up, spray with an acrylic clear coat of some kind. Good luck!
A better, but expensive, solution is to have a professional wheel repair shop do it.
These may help:
How To Remove Corrosion from Alloy Wheels : How-To Articles
2004 American Tradition; 2014 Buick LaCRosse
Homebase in the Ocala Nat'l Forest near Ocala, FL