I seem to totally suck at raising diffenbachias. Both of mine suffer from the same problem, which is that the bottom leaves dry and curl up, and eventually fall off. It starts with the tips of the leaves turning crispy, before the whole thing goes yellow and drops off. I've experimented with light levels, watering levels, spraying every day vs. not, and they just don't seem to enjoy my condo. Our place is angled north-west, so it gets a moderate amount of light, and a bit of direct sunlight later in the afternoon. It can get fairly dry in the winter, but my other humidity-loving plants don't seem to mind too much. Any help would be appreciated.