Hi everyone, I'm currently 6 weeks into my first grow and, as you can see in the pictures, I've run into a hopefully minor problem. Each of my 3 plants have begun to develop these brown/tan spots and purple stems. I've been looking around to see if I could figure out what's going on and so far I believe it may be a ph problem or possibly a cal-mag defiency, due to the organic soil. The following is my current grow setup: 4x4x7 tent, 400 watt MH, 240cfm exhaust, 2 oscillating fans, 3.5 gallon medium, and plants are in a 60/40 soil mix of fox farm ocean forest and Coco pearl. Any help is greatly appreciated.