Browning yellowing sugar leaves

Light burn, light stress, heat stress can most certainly create the type of issue you see here. A quick peek at your diary shows me you have a 1000w light 8 inches from your plant. That is way too close, you should be at a distance of 18 inches plus or minus a couple. @MrGreenMan, its not really good advice to tell someone to add more nutrients just because you're having the same problem and you "think" it might be a P deficiency. That kind of advice is only going to hurt someone's grow, and none of us want that. Happy growing.