If yours are anything like mine I would definately recommend a full de/retension. I'm not entirely sure that you would new spokes but without being able to inspect them it's hard to say. If I was you I would ask a wheelbuilder you trust to detension the wheels, inspect the spokes(replace as necessary) and then retension using new nipples. I say replace the spokes as necessary because the spokes that came with the wheels are DT Swiss Competitions. They are quality spokes to begin with, so the only reason to swap to the X-rays is if you wanted the aero qualities of the bladed spokes. The wheel came with good components it was just built poorly(at least mine was) but once I de/retensioned it all of my problems went away.