I still have the factory exhaust tips and mine also get brown around the edges buy like Mark mine wipe off fairly easily. I think you may have either got a cheaply painted set of tips for they just need a good cleaning.
2011 Cross Roads Sunset Red
OEM short windshield, passenger backrest, crash bars, saddle bag bars, heated grips, vinyl closeouts, tachometer, ambient temp, LED headlight, luggage rack. WD lay down licence plate.