I had granite countertops installed 2 years ago. There is a seam that is right in front of my sink cutout. Over the past 2 years the seam has become uneven. The installers said that there is only a 1 year warranty on coutertop seam repairs so I am stuck trying to fix this myself (or else pay $250 for them to come in and even out a 3 inch piece of countertop!!!) Any suggestions of how i can try to even out the seam again?

There is no visible water damage to the cabinets and no obvious reason that would cause the seams to be becoming uneven. Any suggestions would be greatly appreciated.