//MOST IMPORTANT, i see u have a lot of space left
-lst (read about scrog, make net like this or use some soft strings to do it), then supercropping.
-don't remove blue light, this causes plant stretching (wait until buds will stop growing up, then switch to red light)
-make sure plant have a lot of air movement (when stem trembles from the wind [slightly!], plant must focus on building a stronger stem)
-high difference between day and night temperature causes the plants to stretch
-temp above 27-29C will also causes stretching
-make sure your lamp are in good distance
-if u think that canopy will get too dense start defoliating (be careful, but even if u hurt them i think this is better then light burn)