I should clarify my comments: I too have fed at high levels without any issues except some minor burning at the tips of leaves but what I have learned is that due to dwc is in a constant state of feeding, it doesn't need that much. Yes, of course I am speaking in general terms, strain and other environmental factors contribute to it all, but I ran a few strains where I maxed out at 1100 ppm or thereabouts and ran it later, same exact pheno, at the levels I mentioned above with no drop off (in one case improvement upon) in growth, yield taste etc. Under virtually the same conditions.
So for me, GD touches on it, it's more of a nute efficiency, get more bang for my bucks issue than it is a plant health issue.