its prolly a differnet strain that takes longer to develop, it sounds like it may be an insufficient light source when ur plants are that old and that small. get a HID, then youll see those little girls take off!! u can start feedin em nutrients now that ur 4 weeks into it, i suggest u get ALASKA FISH FERTILIZER, works great, its cheap and 100% organic! give em about two tablespoons per gallon!!