Funny you mentioned run off. My opinion on run off went from thinking it was useful 2 years ago, to useless in the past 6 months to possibly useful again when used right and you understand where the run off ph should be if you know your soil. Not sure yet if it is useful.
I had a theory before as to why so much fighting takes place on this site, wasn't a very good one.
Here is a new one.
I notice my opinion has changed on so many things. Flushing, fertilizing, watering, PH, run off, the cause of problems. All of these things, we are all going through our changing positions at different paces and times and then clash with other opinions.
I learned to manage my garden from books. I had no experience even with house plants.
I have furthered this base grow book knowledge with tons of university ag and container gardening info and now light spectrum confirmation from the university of Utah and Michigan matches the old info in ed Rosenthals grow guide book and clarks marijuana Botany.
The best and easiest info to grasp for me was the education center on premier horticulture ( pro mix) website. Real crop production info and management guides and videos there. Just not for pot.
Anyway...
The point is the info is solid and doesn't really change like you would think from the forums. The reason to have runoff is to help wash away built up salts and the reason to measure it is to monitor trends in ec and ph so you know what your inputs do to the medium over time.
I think we often argue without realizing or communicating all the info about the methods.
It is important to know why. Blanket statements like "flushing is for toilets" are not helpful.
I have been having mag deficiencies for the first time in my system recently and the plants went calcium spotty too. Very frustrating. I check my ec every time but not my ph. I check that with new soil mix only usually and got comfortable.
I found that my well water has gone down from .3 to .2 ec this summer. I assumed I had a deficiency because of the less calcium and mag in the water.
Wrong! I checked runoff ph on a sick plant and it was over 7. Bright medium green with the gh drops. It is always army green or lime green with ocean forest and my nutes and water so....
Higher ph means I was feeding too little. The nutes balance out the water, buffer and plant uptake from raising the ph too much over time.
The plants in question are larger and vegged longer than I usually do. The were hungry and I let it progress. Paranoid I would over feed with such a high dose I don't usually give.
The lower water hardness had nothing to do with it. I leached the pots with fresh well water and raised the fertilizer strength and the plants started to heal the next watering.
They had stalled but will finish fine now.
I will monitor ph more often with the ec of my runoff. And I write it all down to review later.
And watch to see if I will have the .2 water and need more feed for other plants. By the runoff ph. And ppm.
Sorry for the super long post. I'm really high from waking and baking.