When I grow with T5's I keep my plants an inch or so away. I do not let the plants get to tall because T5's have a hard time penetrating anything more than 6 or so inches away. In my experience I would get colas a few inches long and the rest of the plant would be like popcorn. In my opinion a 3 foot plant is a bit big for T5's.
edit: for your next grow I would build a screen the size of your T5 fixture and do a scrog grow.
this is all my opinion other people might not agree.
demoreal Reviewed by demoreal on . Tops are burning. I can't adjust the light any higher. I am using an aeroponic system and I have 12 females and they're all too tall. I am using a 432 watt four foot eight light ho t5 system. The plants are almost three feet each and the light can't go any higher. I cropped the plants a little bit because the tops were burning. What do I do? I keep bending and pinching and cropping and they keep rising. It's the second week into budding. The thing to remember is that the light can't go any higher. Can I crop the Rating: 5