Changing you tuning or string gauge essentially do the same thing: change tension. A set of 0.013's tuned down a whole step will create similar tension to a set of 0.012's. That means that the guitar (top, neck, etc) will react about the same. If the guitar is playing fine than there is nothing else to do. If you are having issues than you may need to have the guitar setup for those strings with that tuning. Depending on you playing style and action this slight change in tension may or may not require adjustments to make the guitar right again.
