[daltore]

Really the only thing I can think of that could be a problem in a series circuit is that you're having the Victor source vastly differing amounts of current that are fluctuating quickly. To lessen this effect a bit, you could add in a medium-sized capacitor in parallel with each motor to kind of even out the current flow a bit. Something around a couple thousand microfarads should probably take care of everything. I could try to do the math, but on the other hand, I haven't taken calculus.