Farmer Bill , I think you are onto something here ---- It's just very possible that once I turned the lights back up full after a period of fully dim, with the lights at full power and the VPD right at 0.98-1.01kPa, the HBSS blew up and out. With that rate of uptake, high rate of growth and periods of pretty high ppfd, could that have over taxed the roots where they couldn't supply the plants with the nutrients it was requiring. The growth was crazy from hour to hour. I could see the difference. ----- Also your Microbe herd may not be at optimum levels ,