How old is the bulb? I believe that an old (over a year) bulb can put out light in the wrong spectrum and encourage more algae than plant growth. That and the color temp of the bulb--which should be around 5000 - 6700K.
Fear is a path to the Dark Side: Fear leads to Anger, Anger leads to Hate, and Hate leads to Suffering.
~ Master Yoda, a long time ago in a galaxy far, far away.