Natural light works fine.

Humidity is just the level of moisture in the air. When the heating element warms the air, some of the water in the bowl will evaporate. This will give you a pretty good level of humidity. The trick is not to have stagnant air. Moisture + heat = bacteria. So you have to have some air flow to prevent that, thus the holes in the tub. Looking good ROBIN!! Crowded is good for babies!!

No need for a temp drop, unless you're breeding. Keep temps steady and constant!!