400 watt HPS is a killer choice, my friend!
1 foot away might be a bit too close...
Also, when your soil dries out, I'd transplant them to bigger pots with more soil.
Your pots and their soil level look a bit too shallow for a 400 watt HPS.
Make sure you keep an eye on the air temp. HPS can heat a growspace to stunting temps.
Hopefully you have a fan blowing?
HPS---especially a 400 watter---should throw off enough heat to dry out the pots pretty fast---usually within a few days.
You are on to a good thing, brother. Try not to fuss too much about them after you transplant them to bigger pots.