I have two rubber trees that I cut from the parent plant at my Mom's office and potted up. Right now they aren't getting much light, as they are being kept in the basement where I am living right at the moment. Every once in a while, a leaf will turn yellow and drop off. I would say (normally) the plants get water ever week and a half to two weeks. Last time I watered this wasn't the case, however, as the plants were bone dry.

What's the rule of thumb with watering them? As they aren't getting much sun they won't be using a lot of water. I'm wondering if there's an answer to the leaf droppage. Is it because of lack of light or underwatering?