If your slurry test says 7.1 or 7.2 then your PH is to high to have efficient nutrient absorption.
3500 ppm run off is more then enough if anything its to hot, but it’s organic so it can run a little hot.
Your soil is currently full of nutrients that is holding a high PH charge.
So you’ll need to lower the PH by feeding something with a low PH.
You can speed this up by reducing the feeds PH to let’s say a PH of 5, feeding a bit and then re attempting a soil slurry sample. Repeat until soil samples are 6.5
Also do a tds test on the slurry sample.
Also adjust your light to the proper DLI
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