Good info. I've rocked several drip dwc scrogs in the past, went to hempy last winter for ease, which I found to be perfect mix of active and passive hydro(which I do hydro in winter, organic in summer months due to temps).
I always keep it lower than 5 plants as it's a misdemeanor. Usually large, pound+ plants in dwc. had two 400s over a single 20 gallon plant at one point. Really came down to a waste of time and space but was a good experience.
I noticed anything over 600ppm under 400s and they showed signs of over fertilizing. Higher light intensity the higher you can run the ppm.
Even with adding ewc teas and decent temps I was getting die off of the bennies causing too much pH fluctuation. That's why aero seems much better as the roots aren't always sitting in water.
I was wondering about you filtering before the pump with dry nutrients. Does green leaf dissolve pretty well? Been hearing good things about them.
You're well on your way to perfecting your environment, and it shows. Keep up the good work