Like I said, I had the same shit - whether it was root rot or some other pathogen. I even had what looked like small green balls (smaller than a BB) in airpockets in the snot. I fought this for several weeks - I'd wipe it off, clean the res, and it would come back in a few days. My plant was just barely hanging on. Whatever it was, adding H2O2 to the res fixed the problem, and my plants lived.
Good luck.
Good luck.