Not gonna lie man, I am stumped on this one. Unless there is Some contanimate in your water that makes it through the RODI that is causing an issue, but without a lab test on the water to know exactly what the 10-20ppm left are, I honestly dont know. If the water is contaminated with some type of hormone or hormone precurser from ag waste or something, that MIGHT make it through an rodi system not sure tho.
My suggestion, use a seed that has been a known problem, and mix your nutes in Distilled water for the entire grow, Only use pH'ed distilled water with cal/mag between nutes for watering and see if you still have the same issue.