Just my opinion, but when I have anything over 240w LED, I keep the power down just a bit, it's more efficient (apparently they say) and I think may be contributing to your issue. I had a SF2000 I forgot to dim once in flower and every plant was green and loving life except this one, I couldn't figure out why. Swore up and down it was improper feeding etc, but something simple as dimming 20% fixed my issue.
This is speculation of course, your problem may actually be nutrient or pH related, but it's best to start at a simple step, see if you get improvement, etc.