Couple more things:

First
Since I just did a flush a few days ago at 3 gal thats way less than the rule of thumb you mentioned at 9. It seems to me, running that much water through a 3 gal pot would water log the roots and cause rot to set in but what do I know. I mean over watering is a symptom right so how do you justify flushing. I would like that explained if possible.

Second

What is a happy PPM on the runoff where is the sweet zone is there a standard for this. Whats considered WAY HOT , Hot ,Medium , and Low. I know where I need my Ph now I want more of an Idea for PPM!

Thanks