My starting mix wasn't optimal as I had little choice in big box stores out of season. I began with a busted bag of Promix Organic Ultimate, some worm castings, and a bit of organic 4-4-4, which I only used sparingly in one pot near the bottom. When I realized I wouldn't have enough to fill all the 3-gallon pots, I bought some coco coir bricks (one from AC Infinity and another I don't recall). When the plants were ready for the 3-gallon bags, I laid the bottom with some coir, then added worm castings, placed my 3D printed waterer on top, and filled the rest with the mix of bag soil, coir, and some more worm castings.
I haven't used any additional nutrients other than the aquarium water, which ranges from 200-300 TDS depending on the tank. I've been adjusting the pH to 5.8-6.1. I bought some Cal-Mag Plus and a 3-part Floracal for after flushing the fertilizer out of the soil, but I couldn't finish the flush due to a lack of enough RO water.
Plant 3, the smallest one that started later, has shown significant growth after the recent flushing and is now nearly the size of the other two plants in just this light cycle. I ran ten gallons through Plant 3, and it had the highest tds runnoff. After 10g it was was still at 530 ppm (from 900). The known female plant didn't get a full flush but received some clean water.
The second plant received ten gallons of flush water, reducing the runoff ppm from 890 and was still in 500's at the end. I think it might take around 18-20 gallons per plant if not more. The pH going in is measured at every feeding, typically ranging between 5.8 and 6.1. During the two flushes, the pH coming out was 5.9 and 6.2.
I have an old soil pH tester from my vegetable garden days that I'll use to check the soil pH today.