Button overlap?

I am working on a map of the usa that as you roll over each state the name of the state appears and the state is highlighted. I had no problems until I was done and tested it. Some of the roll over parts of the button (the text of the state names) fall underneath of the button (state) right next to it. Why would the rolled over button be affected by the untouched button to it’s sides?

I do have all of these buttons on the same level and they are close/touching each other. How do I make it so that the button that is rolled over and it’s text are in the forefront and exposed?

Any thoughts? Thanks.