how far are you keeping the light? That light (floresnt ONLY) should be real close to your plants like two inches or a bit more. That will make the plants grow with nodes closer together. Also putting a slight breeze from a fan on them will also make them have stronger stalks. You can also do a thing called super cropping. Look that up in search here, i would think there would be directions on how to do that (not sure what age you start that). You can also use the long plants to good avantage by tying them down and do the LST (Low stress training, you can look that up here too).
Good luck to you....i'm sure ms. attic will be by shortly. She may have more ideas for you.

Please do not burn your plants by putting your HPS light two or three inches from them, i was only talking bout the floresent light being that close.
inbud Reviewed by inbud on . help stinkyattic!!!! why are my plants skinny? this is for anyone that knows there shit about growing the good stuff.. but stinkyattic it seems like you know your shit. i've been growing indoors for a couple weeks now and it's not going very good......theyre about 8 in tall and only have about 4 to 6 leAFs on them a piece on have a hps light and a regular florecent with grow lights in it... the ph is around 7, the temp is usually around 85 and the humidity it around 50%.. the only a couple weeks old and they cant even hold themselfs up... Rating: 5