7 week old LSD is looking great, but a few leaves are showing yellow spots. pH has been steady and am using the GH grow schedule. I vegged for two extra weeks. Humidity might have been too low, maybe light burn? Using luminous COB's at 50 watts per COB about 22 inches from plant, 4 COB's total in a half of a 4 x 4 grow tent. Just trying to figure out what is causing this. Thanks.