Wow....wait a minute. What kind of light are u using. It is too close if your using any hps light or HO cfl bulbs. If it's a single or 2 light bulbs cfl then your ok at that distance maybe go to 9 inchs away for a couple/3 days till stressing stops. Make sure u use the pick up pot check weight to make sure it's on the light weight side before watering. never used your soil but should be ok if it drains well. If this kind of issue continues try FFOF soil. Does a major improvement on most all grows...specially newbees...reuse the soil as well....another topic.
think this way...always go less when plants show issues other then lush green plants swaying in the wind.... not more of anything....water, light, nuts. ect. When plants look good is when you can ad things to try on a nice looking plant.