sorry for the delay, just too damn busy!
...dead roots would explain most of this for sure, though that ratio is like a bloom booster, not a base nute for bloom or especially growth! Too much K will screw with uptake of some other nutes, and can become toxic if overdone,... Again, what are you foliar spraying with? Than can overload things too if too strong, or frequent...
-- ah! OK, if you're getting foul smells, the roots and the solution are contaminated with bad microbes, and likely damaging the roots too,.. might be pithium rot, but I'm not a hydro' guy, so research that more here, ask around in the hydro section,...