I would suggest getting some extra lights for your trees. Total cost was about 25 dollars. I leave the light on from 14 to 16 hours per day, and keep my plants as close as possible to the tubes. Indoor plants also need different watering schedules than outdoor trees. In the summer, when most outdoor trees are growing vigorously and have nice warm breezes and a nice bright sun, they will usually need to be watered everyday.
Indoor bonsai are in very different conditions.
A special thank you to Hud Nordin for the following list of indoor bonsai. Juniperus chinensis var. Juniperus chinensis var. USA Bonsai - Zentrum Muenster Wolfgang Klemend Weselerstr.