what i did with my hydro set up---> they got too tall. i grabbed a rock (about the size of my fist), tied some thin rope around it, and tied the other end to the top (LOOSELY), like tie a loop at the other end with the top inside the loop. **dont actually tie a knot around it**, then put the rock to the side, so the plant goes diagonal a bit, dont bend the plant, just give it a 'lean', a couple of days later, tighten the rope a bit, youll notice the side branches turning upwards on their own (thats good = more yield) i ended up with 5 big ass plants all leaning over and their branches going straight up.
the only other thing to make sure is that they are getting ZERO light during flowering dark periods.