They are low maintenance with exception of my airstones getting clogged. My DWC which is actually called bubbleponics and holds 8 gallons of water but only using 6 gallons. I do have a plant in a 5 gal bucket and the root mass consumes half of the bucket, your roots should be the same in a few weeks. I also use Hempy buckets which is really simple to grow in, you can look them up on the internet. My pineapple express is growing in one now, uses way less water and nutrients but must keep the nutrient well clean and fresh, that's where the Aqua Shield comes in.
MHO, when growing autoflowers, keep it simple, don't experiment, less is good, if your ppm's are dropping then you need to increase it, the plants need more food . Your readings look good, the cooler you can keep the REZ the better. I don't know much about MH or HPS lighting, I use CFL's and high powered LED's and I get good results so far.