The easiest way to know when to water is to weigh the pots with soil when they are dry. Then water them. When they get back to the dry weight, water again.
I think one of the most common problems is overwatering.
You're not going to get fast-growing plants with no fans and only CFL light. One of the reasons why your soil is staying wet is because the plant's processes are not firing on all cylinders, so-to-speak. They're waiting for more light and more air movement -two things that you almost can't overdo with cannabis- so that they can start transpiring the water you give them. They need water, too, but it's better to make them wait for it until they are really thirsty. The only way to tell for sure, with soil is by the weight. If the soil looks dry but the pots are still heavy, then don't water them.
You can get far better results by under-doing it on the water and overdoing with air movement and light.
