Mine do fine at 1,200PPM with no discoloration. But the plants are massive and seem to thrive at that PPM. That's why I said +/- plus or minus. I realize some strains may not thrive at 1,200 PPM water but mine do and that's what my manufacturer's advanced nutrient schedule ends up with if I follow it. Mine are four weeks into bloom with massive nugs, probably a pound per plant when they are done. I've seen people on here post that they use 1,600 or even 1,900 PPM without nute burn, so I figured 1,200 PPM was pretty modest.
But yeah, if my leaves were showing signs of nute burn I would back the nutes off. But if you back the PPM down too low in the middle of bloom, the leaves will waste away as the plant starts eating itself.
Fortunately with DWC you can find that perfect balance and correct it quickly and easily if it goes out. Worse case scenario you flush the bucket and start with fresh nutes.