NEW YORK - Kelly Clarkson has married music manager Brandon Blackstock. The pop singer tweeted a photo Monday in her wedding gown next to Blackstock. She writes, "I'm officially Mrs. Blackstock." Clarkson says she tied the knot Sunday at Blackberry Farms in Walland, Tenn., outside Knoxville. A representative for the singer didn't immediately respond to an email seeking comment about the marriage.