a strong bulb is a hot one. and more bulbs is even hotter. and when you are cooling your area your plants like it but your bulbs don't. your bulbs are cooling and getting dimmer. its a must to try to keep the bulbs as hot and bright as they can get. even a regular 14'' fan will lower the lumens of any light. air circulation must go upwards off the lights so the heat goes that way to help keep the lights brighter. Have a look at these girls ripened full of buds ready for 12 hrs sleep smothered by walls and ceiling with flourescent grow bulbs of every spectrum!