It is probably 8 inches from the light source and the light is really powerful. 600 watts. Maybe it is burn? When my first two plants started dying (from the same symptoms) , I had 2 more sitting under a different light that was only 150 watts and they were PERFECT. The one turned into a hermaphrodite do I harvested it . And the other one is the one you are looking at in the picture above.
I have another one flowering right now next to the one in the picture and it is doing fine after I added the cal mag to its nutes. If it grows up and starts to run into the same issues as it gets closer to the light, I guess that will tell me whether or not that is the problem.
I did not use perlite, just coco. I drench the container with nutes though so I am pretty sure the nutes are getting to the roots. I usually only water every 3 days or so because it takes that long to get dry enough to justify watering again ( when I say watering I mean water with nutes). I added cal mag to the nutes for the smaller plant and the one that is dying. It didnt fix the big one though. I also fixed the PH. I realized after testing it that the PH was insanely low in the nutes I use for flowering. I had to use 5 times as much PH up as I do for vegetative nutes, to get it straightened around. The water was murky because of the nutes so I am sure it is not perfect PH, but it is a hell of a lot better than it has been in the past.
Thanks a lot for your help guys. I have spent thousands of dollars and over a year trying to get even one harvest and have had no luck yet. I just keep running into problems. You guys helping me really helps me keep my head up and hopeful that they will work out eventually.