For the record, the tray that had the "curl", I had 8 Poison Kush and 1 OG, the OG didn't curl at all. So obviously it is going to depend on the particular plant, but I could only guess it was from lockout because nothing else made sense. Now that I have put a few strains through the mix I am finally settling down on a few so won't have to mix batches for long, so plant specific nutrient needs will be easier to determine.
Very interesting that it seems to be light based on your setup. I wonder what that is. Mine was under the same HPS for whole time, but I had a batch of poisons go through that looked fantastic 2 weeks prior. Rawr, I don't like these kinds of mysteries, I don't want it to happen again.