autofocus - Why are photos taken with my old lenses all out of focus on my new Nikon D5300 body?

My Nikon D80 died, and I was bought a new D5300, body only. All the photographs are out of focus when I use the lenses I used with my D80. Why would this be?

I'm using the Sigma 18-50 f/3.5-5.6 DC, Sigma 55-200 f/4-5.6 DC and Sigma 70mm Macro f/2.8 EX DC lenses.