If you've bought some bagged compost, and it says it contains nutrients for 4 to 6 weeks, then use water only for the first two and a half to three weeks.
Cannabis eats more, than some flowers your mom might grow, or more than the average garden vegetable. Your soil should be moist, but not wet. IME it doesn't hurt to let it dry out a little between waterings, that promotes more root growth. If overwatered, roots don't fully develop, because they only grow as far outwards, and as much volume as necessary to find water & nutrients.
Ionic is a good brand, but kind of pricey IMHO. I like Earth Juice, Age Old, and Blue Mountain Organics (Ebay). BMO has a combo pack that runs about $ 35 shipped, with a root inoculant (beneficial bacteria and fungi) grow fertilizer, foliar, and bloom fertilizer with good numbers for growing cannabis.
Here's a link to an info only site about there stuff, it has a recommended feeding chart also.
http://www.angelfire.com/ar2/tts/bmo.html
There's a guy who used to come on here a lot named Ohsogreen, look for threads he made about growing organically. He actually got me interested in the SPT, and I'm glad I tried it.
Dry ferts like Epsoma brand (Lowes, Home Depot), along with some SPT will get the job done also, and cheaply. Bottled or dry, decent nutes are decent nutes. To me decent means, not made from petroleum, the reason I only mentioned those three brands.
If you're lucky enough to live near any farming communities, the cheapest ferts can be had for free: Rabbit manure, Cow manure, Chicken manure, Horse manure, etc. Just one word of advice, compost all of those before using them, dry as top dressings, or in teas. That way they don't burn your plants.
Quoting that guy " Low, slow and steady feeding works best " I agree
As far as lights go, using both from the start would be best. More light equals more growth, and you need to change out the air in your closet as well, otherwise the lack of CO2 will slow growth to a crawl.
I'd go with the two lights you have, and add a third 2700 K bulb, when I dropped the light schedule down to 12/12. Then you'd have a nice mixed spectrum, but one that was predominantly flowering friendly, promoting. That would also ensure you had enough lumens, so you don't end up with a thin, stretchy plant, with overly airy buds. Good luck, and don't worry, good buds can be grown with CFL's, and good nutrients.