The photos DO help Mr M....thanks. You know my numbers never go above 1350 during my whole grow and from the looks of your they ARE overnuted and unhappy looking.
There are two things I think you need to do and they are keep your ph in check (between 5.6-6.2) and keep your ppms lower than 1000. I would drop your number from 1200 to 800......you need to give them more water than food at this point. My hydro man usually has me drop the ppm in half (to about 600ppm) if my plants are sick......it will ease the stress and help them recover more quickly.