If your buddy with the crazy cocktail is running canna that would not surprise me; it has seemed very forgiving to me- I've run their hydro nutes.
IF you have a wetting agent by all means use it, or add a drop of dish soap to the sprayer.
You're not running RO water by any chance?

Can you give a rundown of what the plants have had done to them (feeding, flushing, repotting, whatever) in the past month?

This is an odd one. Almost as odd as The Gipper bottle-feeding a chimp. But not quite.