The first thing is going to be make sure your lights are kissing your colas, put them within an inch of the lights. And you really should upgrade your lighting, that is your biggest problem. I'm not sure a 150hps will need a ballast or not. But i'm pretty sure you can get really affordable 250W units, for like 150$ - 200$ that would absolutely increase your yields.
Also fresh air is very important. Along with proper co2 levels. If you have no fresh air, your co2 levels could be as low as 50 PPM. Plants live in a normal 300 PPM environment, and will thrive in environments with a PPM of up to 1500.
and last but not least, expect roughly .30 - .50G per watt of light, on an auto, Done correctly.