tinytoon, I have a GB Instruments GMT-319 multi-meter; but I am not sure how to use it to measure EC/PPM (if I even can measure electrical conductivity in my water with it). Advice?

Well, it's been half a day with the new "hard water" nute solution, and I see no reside building! Hope! But I'm afraid the plants are so far gone that I'll have to start fresh to really test this.

Is EC/PPM a big enough factor given my situation so that I ought to get a read of it before re-starting?

Thanks!