take a pic and post it so we can see. A 400 MH should be as much as 30" off the base of the net pot. It produces 10K LUX at 2' and you only need about 3500 LUX in veg, so don't be afraid to lift it.

One tbs/gallon does not seem like to much, but can't really tell that way because each nute has its own schedule and concentration.