Thank you all for your above comments. I use K-Lite from First Ray's, 150 ppm weekly. In the winter, I reduce the ppm to 75. I add the First Ray's kelp 1 tbsp/gallon monthly. I grow on 2x4 ft shelves, under two 2-bulb LED shop lights (so 4 bulbs per shelf) and the plants are about 8" from the...