Indoor OG Kush

Growing nicely; may have to raise the light by the end of this week. The weather outside still on the cool side which keeps the tent humidity low; well, except for a brief spurt into the 90's. Am keeping an eye on it--if I have to run the exhaust fan 24/7, then so be it. But everything good for now. Update: three days later I find one plant is exhibiting a bronzy margin around the leaves. I wonder what this is? I hope its not a deficiency--this is only on one plant.