My thoughts...
1 - bigger buckets for bigger roots,
2 - i've had a fairly long period where water temp was above 23C, so they were affected a little by root rot,
3 - since adding an extra airstone per bucket, roots have grown back by *a lot*
4 - when I checked the far right one (tallest), when putting it back somewhere accidentally it took a little bit of flowering bud (smoking that was nice though, got a nice high off it)
5 - i need a more powerfull light covering a bigger area; current LED is rated for 80x80cm footprint, but as it is i can't complain too much. The space they occupy now would be around 80x80, with the extra room used up by the main res & fan.
i think, if i used soil, i could have gotten another 2, maybe even 5 plants in, but would have been wishing for a better light even more.
overall, they are doing well considering the limitations of light and issues i had with the roots.