Thanks for all the replys.
Pablo, why don't you think the sodium is not all native? The Clean 7500 has ~260 ppm sodium in a VOA. That doesn't account for the potassium though. I have another load of Clean 7500 in there. I think I will do a quick flush with a dino like Trop Artic or something that doesn't have any sodium in it according to the VOAs that Butler Cat posted. This should get most of the sodium from the Clean 7500 out of the engine. After the flush, I will run it 2 - 3,000 miles and test again. Does that sound resonable?
I haven't noticed any drop in coolant levels in the radiator itself or in the overflow tank, so if it truly is coolant, then maybe I caught it quick enough since the wear is as good or better than before. The Clean 7500 provided the same wear protection as the M1 for less than 1/2 the price.