Hmmm, I would print one of the 2 colors that is in register as a baseline, then adjust the 2 that are out, and see what happens. You probably know the obvious things like are all the knobs tightened and the like, but when you're under duress, the simplest things can be overlooked. Vastex makes fairly solid stuff (I started on one waaaayyyy back) so hopefully it's something simple...
Steve