I was keeping my 400w HPS batwing at about 18". Granted, being in the desert I run a bit higher with temperatures, but in the winter I was keeping it to about 12-14". Are you familiar with the 'back of the hand' method of determining distance the light should be? Likely the light is too far to promote growth in your original leaf. Maximum effective range for a 400w is about 3 feet, but you don't want it that far away. The closer the better, without burning anything.

Would pick a medium and stick with it. Makes life easier if you run into problems. Same with the nutrients. You'll want a growth nutrient for the veg phase and a flowering nutrient for...flowering. The main difference is in the N-P-K ratios.

Nutrients don't last long once in water. Are you mixing nutrients every day?

Are you using your nutrients to adjust the ph? If so, there is a better way. (phDown)
What if they need more water on a hot day? Or less water when humid? Are you going to overdose or underdose 'em? Not a good idea. When you follow directions and feed per provided schedule, you get the flexibility a garden demands over the long haul.
Mixed nutrients should be used asap. If left to sit-out, it begins to degrade.

Painted the floor, too?