Your plants should have a little more stretch to them and depth of cola.
With a 600 watt HPS you should be killing it. Like three pounds a run or so with just a medium producer.
I like the 600 a lot.
Many are growing on here for the width of canopy and not the depth of the canopy.
Light intensity, penetration and equal distribution of the light , along with constant steady airflow through the canopy will develop the buds deeper into the plant, you can not have a canopy so thick the light can not penetrate it though or the air.
The fan leaves are the solar panels that develop bud, these fan leaves develop along the terminal stems just under out cropping Branch's . If you remove the branch and leave the terminal stem with the fan leaves on it and pinch to top for five weeks in a row you will divert the energy the plant has from the end of a very small branch to the terminal stem feeding the bud site with a lot more food and water allowing the light tonpentrate deep into the plant to allow a large bud developing instead of a small bud developing out at the end of a small branch full of crappy leaves , this also allows the light to penetrate.