I do not find the plants get stressed by my method. The PH is always in range 5.6 to 6.2. Letting it wander will allow the different nutrient to pass through their sweet spot. Letting the PPMs cycle does not hurt them either as long as they are getting enough. Using run-off for anything is a bad idea. I have had run-off readings as high as 2000PPMs when in the root zone it was 500PPM Just worry about what you put in. Yes I have drippers 1 GPH pressure compensating so that each plant gets nearly identical fertigation amounts. It is not perfect but very close.