What strain are growing? Did you buy them online? Are you using feminized seeds? If you throw them into 12/12 to early it can cause Hermaphroditism or plants with both sexes and can go to seed. Jorge Cervantes recommends that you what until the plants show preflowers which usually takes about 2 months and then veg for 2 more weeks before changing to 12/12. Veg 'em in 1-2 gallon pots until they show there sex (If growing regular (Non Feminized) seeds get rid of males at this time). Then put 'em in 5-7 gallon pots, veg 'em for 2 more weeks and then start blooming cycle. But if space is an issue and you may want to try one of the auto-flowering Strains. I recommend Dutch Passion autos like these:
http://www.dutch-passion.nl/en/seeds/product/think-different/
http://www.dutch-passion.nl/en/seeds/product/automazar/
http://www.dutch-passion.nl/en/seeds/product/autoblueberry/
What Soil are you using now? Normally you would transplant into the same soil you started with? But if you're looking for a good organic soil I would recommend foxfarm, roots organic or Black Gold
http://foxfarmfertilizer.com/products_soils1.html
http://www.aurorainnovations.org/soil.html
http://www.blackgold.bz/products/potting-soils
Choose the soils that say they are designed for better drainage and aeration. Or add your own extra perlite. Don't use more than 33.33% perlite or it could stratify and your soil will float!
I recommend these fertilizers
http://generalhydroponics.com/site/index.php/products/general_organics/
A 250 Watt HID should probably be about 1.5-2 feet from the plants or high enough that it sheds light on all the plants.
A good way to simulate a more natural growing environment and encourage earlier and stronger preflowering is to start at 22/2 photoperiod and decrease by one hour every week until you reach 12/12
Week 1----Week 2----Week 3----Week 4----Week 5----Week 6----Week 7----Week 8----Week 9----Week 10----Week 11
22/2--------21/3-------20/4------19/5-------18/6------17/7-------16/8-------15/9------14/10-------13/11------12/12
Hope this helps. Good luck!