Humidity was a bit too low for my taste this first week so I turned off the 150W big lamp as it was warming too much the environment. At this time I was also putting too much ventilation to reduce the lamps temp (lamps are fully passive); this was driving humidity even lower and it was also increasing temperature at the plants level because the airflow was directed towards the plants, moving hot air to the ground. I changed all this in week 2 (this being just my second crop).