I've seen that same issue with the plants looking burnt in my previous grows. I also grow in organic soil and I also use
Spider farmer but the
SF2000 in a 2x4. I noticed during the winter when the temps were cooler the flowering plants were thriving, however in a different run in the spring /summer the temps got around 80 to 85 degrees during flower, and the plants looked like shit.
My guess is the temps and the intense light is what is affecting your plants, although i do not know your exact environment. Could also be the genetics too since some are more sensitive to temps than others. I believe for the
Spider farmer quantum boards it is recommended to have a distance of at least 18" from the canopy during flower. Its hard to say whats really going on tho since it could also be the different nutes.
By no means am i an expert, this is just based off my personal experience. Hope you get it all figured out