My JCW rear bumper has 2 grills in the lower side and the grill(actually black dots are printed on silver aluminum plate) has been already discolored(yellowish,,,). I installed it at the dealer last June. Well, it's still about 4 months old...
Any one has the same issue so far???

I need to talk to my dealer if its warrenty would cover it or not...

 

There are no JCW parts for the the rear bumper. Are you sure its just not the stock bumper parts?

 

I believe you are talking about the decals installed on the rear bumper of the Aero Kit. My is getting discolored as well. But I know if I say something they will probaly blame it on my aftermarket exhaust.

One NAM vendor sells replacements:
Cooper Flags

 

Actually some people(even dealer guys) says JCW aero bumper instead of Aero Kit. That's probably because JCW democar comes with aero kit as well...
Anyway, it looks like original one is less resistant against UV. It's really quick to get discolored.

Now, do you think Mini will accept to replace those grill?
Well, it will be no meaning to ask because even replaced one gets discolored quickly ubless Mini improved the material.
Other option is to replace them by after-market grill for the aero kit bumper.
Anybody knows any after-market Aero kit grill ?