Anyways

the prob is that your flowering nutes are acidic, which brings the ph down. you compensate by bringing it up for your plants. now your plants use some of those nutes. well, that brings the ph up. now you have to add more ph down. they are right, a larger res will do wonders, despite gh's 10 foot tomatoes.

You could always change res every 2 days, and eliminate the prob, or discard runoff and refill the nute res from a 50 gal drum or something. Without these kinds of measures, you will just have to keep adjusting yer ph.

Also, do you check the ppm of your solution? I bet it dives quickly with that res and that many plants. Just a thought.

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