Perhaps you have a clear plastic chainstay protector that's dull ? Chainstay protectors are a good idea on non-fixed bikes to protect from chain slap.
My '09 CAAD9 has a clear chainstay protector. After ~5k miles, it's pretty chewed up, and there are nicks where the grease doesn't come out. It's kinda obvious on a white bike...also have some damage to the clearcoat on the top tube. I didn't buy it to shine it, I bought it to
ride it.