and if you want to know what i mean by that.... ill elaborate.
co2 and other additives are like icing on the cake. it goes on last. cant add the icing if the cake is still baking.
-what lighting are you using? if you say cfls, you might as well forget about it.
-how stable is your environment? are you keeping ideal temps and humidity levels? if not....forget about it!
-what is the feeding schedule?
and btw, those makeshift co2 rigs dont work....you may think they work, but its just a placebo! aint no way in hell a homemade co2 2 liter will put 1200-1500 ppms of co2 in your grow room air