Your plant looks happy and healthy, but IS a little short for her age. As others have mentioned, some strains, kush included, are usually compact and bushy. They often take off growing taller later in vegging, but you don't seem to be enjoying that luxury. As @Dabfarmer said, side lighting might help to encourage it to grow taller. I would pinch/top it to encourage more side growth as well. Thiose huge fan leaves are shading the growing tips below them, which is often where you see a lot of growth. You seem to have enough light, but maybe it isn't spread out enough? I've never used lights like yours...I think additional lighting would benefit you greatly, but you seem to have mastered the growing part so far!