Personally what I do is whenever my plant gets around that size depending on what I want the final structure to look like (am I promoting branching or going for single cola?) If promoting branching take the 2 big leaves out in your picture that point left and right. They will most likely have nodes pushing up underneath them. By taking the big bbn leaf out that's shading it the node will be able to stretch out towards the light where it can properly develop. If promoting single cola I would recommend not defoliating and instead just lollipop enough of the bottom of the plant so you arent splashing water everywhere on the lower parts. Then if you see a branch growing out snip it off because you're trying to promote top vertical growth.