Light quality can also play a part. If there's not much natural light coming in the table (and let's face it, dull days with all the rain and cloud, and darker mornings now), then I think some torts will struggle if not now but in due time to go about their routine.
If the table is a bit on the dark side, and the light quality from natural sources is bad - IMO you might need something to stimulate - such as an additional strip?? Or daylight bulb..
xx