There are any number of techniques you could use with photoperiods... the simplest being LST - which is gently pulling the lower branches out away from the main stem so the bud sites on them receive more light. Many folks will tell you to top them which will get you more main colas but this needs to be done when they are young - when they've got 4 or 5 nodes. There's also mainlining and fimming but I'm totally unfamiliar with those techniques. I would research the different techniques (YouTube has a lot of vids on how to do each!) and decide which of them you will feel comfortable trying... and you can combine techniques as well... Each is designed to produce more bud sites that have more access to light which in turn will produce a larger yield.
Good luck - THIS grow looks great!