Bacteria won't really increase EC, what you'll see when they have a bloom event is pH rising significantly, and fast. That's part of why I quit using
hydroguard, it's too much a pain in the ass to run live imo. Most of all my pH issues went away as soon as I switched to h2o2 -- just my experience though, wouldn't recommend changing anything just yet until we identify what the root cause is.
That pic looks suspiciously like a calcium issue. Leaf twist + deformation is a sign that either ca is being locked out or an over abundance of silica is present -- i doubt the latter because silica tox does some really wild shit to leaves.
I'm leaning towards pests because of the structure of the pit marks on the leaves. Some of them look like holes, there are random white specks all over, and just the overall shape doesn't strike me as a typical deficiency or lockout symptom. They're too round, if that makes sense. Having confirmation that you did have an issue before further makes my intuition think that. Could scope the leaves and see if you find any creepy crawlies running around just to rule that out entirely.
You obviously had some nute burn as some point as you've mentioned. Further, I'm thinking because your water level is dropping, EC is rising, pH is rising, the plants are being attacked by something preventing them from consuming what you're feeding.
@PK1 you've the DWC experience, what say you?
@Dirtbag have you seen anything like this before?