Do I have to tell you why again? Your lights are shit to reduce yield and you are not giving enough nutrients to support those new tops.
You can top during any time before new sets of leaves are not growing. That means the plant has focused 100% on making flowers/buds.
Deza, You can do whatever you want to them, those babies are your plants. Weed is the shit and I don't plan on ruining any..
Some of you think I am a dumb ass. My techniques I said before are for you, If you want to decide and try an experiment on just ONE plant. Then later during harvest you can compare your plant to the others. What I said doesn't hurt any one or thing. Maybe all of crackbaby's plants came out crap because he did not leave one plant alone and was so stoned to tell himself topping is useless.