400w HID indoors questions about nutes/watering/lighting

Thanks in advance for any help....

To start, I have an underground cellar that's about 14' x 7' x 7' that I'm growing in. I have a dehumidifier and an automatic watering system.
I'm using 10" pots as I plan to flower fast. I'm also putting a small area for a mother to grow with it's own fluorescent light but I'll deal with that later.
I have some pics of my setup now...
The first is the watering system. Next is the 12 pots, then the secondary lighting and again in the 4th, last is the whole grow stand. Keeping the pots about 6" off the ground.
The 400w HPS is right in the middle and is going to be about 18" above the tops of the plants. Ignore the plants that are there now, they died from over watering
The 400w HPS is a tube style and I have a 6" fan pulling outside air, pushing it through the light tube and then going outside to cut down on heat.
The fluorescent lights are 23w but 100w equivalent full spectrum bulbs.
So my questions are.....
How do I make a good nute mix?
with only 10" pots I can't let them grow forever cause there won't be enough room for the roots, so how long should I let them veg before flowering?
What would be a good watering/nute schedule?
Any other advice would be appreciated as well!

just an initial observation, It seems the grow area (not the cellar) is much larger than your light can handle. 1 400 HID can cover maybe a 3'x3' area and the light should be much closer than 18" once they are rooted and growing well. They should be as close as you can get it without burning or causing heat stress. There is a square footage and light coverage chart floating around as well as a distance from plants and lumens chart. How long to veg is personal preference on what your goals are. You can let them veg until they are 12" tall or greater - your call (even shorter than 12"). Your nutrients and schedule depend on the medium and style you grow in and with. There are ferts for soil and soiless and both. I am no expert by any means but I would try and keep things as simple as possible, maybe less plants until you have some success and can see how they react to what you do ie. water, feed, lights, environment, etc. Might want to consider a hempy bucket style - have heard good things about them and it is supposed to be a passive hydroponics type system (hand watering) but yield good results for "non-expert" and "expert" growers alike and it's pretty straight forward, simple and cheap. Best I got.

As far as the HID, I know it only covers a smaller area, like 4x4 I was told. That's why I have the (6) 100w fluorescent lighting as well around the edges, to make up some of the light that isn't getting to the edges. I've tried this once before and I way overwatered and killed them all. I was watering twice a day on a trickle system(same one as above) for 10 minutes each time. The pots are off the ground about 6 inches and drain well but I know that it was way too much water now. I've read to 'listen' to your plants' needs and water accordingly, like twice a week roughly or as the soil completely dries out. I'll move the HID a bit closer from now on as well. With only 10" pots, I don't plan to let them veg very long, maybe 2' if I can get them that tall and start to flower at that point.