How to clean a cloudy Granite (http://tanbrown.org) /resin sink?

I have a black composite, Granite (http://tanbrown.org) and (http://maplered.com) resin, sink in my kitchen.  One side has turned cloudy.  I have never used abrasives on the sink so it is not scratched.  Does anyone have suggestions about how to clean this sink?  It is two years old.