If this is the mini-garden I believe it to be, I'd definately recommend looking at the FIM technique, and apply it now, given your clear limitations on space... And take it easy on the watering and nutes for now... very easy... Thatz the first thing that so many beginnerz mess up on, is their understood impatience with growing, thinking that "just because I give it food and water, it should grow faster"- And it couldnt be farther from the truth... Read as many High TImes as you can, namely the Grow Room Q and A section, and research the hell outta what you r doing... This site is a wonderful resourse for the novice to most advanced and experienced growers... Good luck, and good growing... P.S.> I'd really give some thouoght to a larger space if you can, and MH and HPS lighting, as well as good ventilation... But, I reckon you'll get there if you were meant to get there eventually...-and to answer your question, 8 weeks from sprout day is usually the window that the pre-flowers will show... Dont pull anything too hastily... Research sexing cannabis... And prune that thing before it outgrows the box, not to mention it'll double or triple your yield...