Ok so I’m just going to throw this out there then just in case no one comes along with any advice and you’d like to roll the dice.
CAUTION: Don’t take my advice. Haha!
But if what you guys are saying is true, then it sounds like you would feed these 4 plants just like you would a single plant DWC bucket. If that’s the case then I’d go with like 5-700ppm and 10 mL calmag for starts.
This is a great chart to go by Rex, I had to dig it up because I haven’t used it in so long but it really does work.
This chart will tell you exactly what is happening inside that bucket via water level, ppm, ph, and it tells how to move forward with your symptoms. Hopefully this will be as useful to you as it once was to me