Focus issue on a D7000

I've had my D7000 now for about 1.5 years. When I first got it, I didn't notice any focusing problems. But recently, everything is soft.

I used one of the focal testing/setting tools, and I can only get approximate focus when the focus adjustment is at the -20 setting - the maximum - using a Tamron 28-74 f2.8 lens. Using my 50mm 1.5, it's set at -15.

Is this something that can be fixed? If so, do I return it to Nikon, or can a local shop do the repair?