Have some pictures from awhile back when this problem first started, figured I would add them to add to the collection of diagnostic pics in this thread. These plants all were netpot-less, just held up by wire. As you can see, there is a thick slime covering the stem above the water line. Oddly, the roots IN the water were OK, no slime on them, but the plants wilted and died overnight from the slime on the stem, it was actually inside the stem also, where the main stem turns into the smaller roots, it was all up inside the crevices and when broken apart, the inside of the stem/root area was black and the slime STUNK horribly.
A lot of the slime problems here talk about the roots IN the solution being slimes, so maybe this is a different type? Also leads me to wonder about what some have mentioned, that it's in the AIR and not the water necessarily. Odd stuff.