what's wrong?
i can only guess stature? could just be a runt... could be a little too much light at this point... allow the length of internodes to dictate the amount of light you give... you can either dim or raise light to affect intensity on a particular plant. can raise/lower plant too.
try raising the light 4" and see what happens. i bet those nodes will experience some "good" stretch... if you observe it stretching too much, bring that light back down a bit.
Looks a little stocky, and if that is your concern this will help. you'll want that intense light as it finishes off vege growth... those last few nodes will stay nice and tight and forma big ol cola for you. intiially you want the axillary growth (limbs) to spread out a bit so there's room for a bigger yield... autoflower allowing... they are on timers and we don't have any control over it beside keeping it happy.