12/12 won't hurt them one bit. Good choice on the CMH. They're highly efficient and produce lush growth. 360ppm is absurdly low. You should be watering in around 700ppm every 3rd water cycle. So feed, water, water, feed. You may just be developing deficiencies due to the plant's lack of available fertilizer. I would suggest you switch to 12/12 and increase your feed days to 700ppm on a feed, water, water, feed cycle.