flying, did you have a fan on your grow? and how do you use soil in a hydroponic system? If the dirt was completely wet at all times you were over watering. You want them to be as dry as possible as often as possible. Mold is of course undesirable, but it's not the end of the world or the grow. You can always spray a fungicide, or just start ventilating and stop over watering. Nothing wrong with 50% humidity, since I grow well in 30, and perfect is 60. If you want to alter humidity you can use a humidistat to control fans, or put a humidifier and a dehumidifier in the same room and let them fight it out.