Depending on strain you can usually get about a pound per 1000 watt lamp. Sometimes more!
I will say you have topped your plants more than I ever would, 2 to 3 times at most.
I top once at around 12" in veg and start bending branches, creates lots of arms without the problem of creating a ton of smaller tops, every time you bend a branch the plant will make the next biggest arm in charge until you bend that one and on and on. This is the effect you should get after about a 2 month veg. These are 24 days bloom today.
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