Are you into flower?? The plants really start sucking up the water when they flower. In my case as well, I have the HPS and probably need better ventilation plus the de-humidifer running (had LOTS and LOTS of rain so far this season; been playing havoc with my grow room)...Looking good man! Buds are coming along nicely.
Whats the deal with hard crusty soil in a day from watering? That's what i'm experiencing at the moment.