I've got an 06 Trek Pilot 2.1 painted white. On my top tube, I began to notice that some of the white paint has turned yellow. It's very noticeable. I was wondering if anyone else has had this problem. I tried to clean it thinking it was just dirty, but it isn't. It is either stained or discolored. Any help would be appreciated. I'll try to post a pic when I can.

Thanks!