Thanks for the thoughts! While I agree plantladylin's humidity suggestion might not be quite on, it did make me think about how even with the heater going the house isn't all that warm. California houses really are drafty, plus we don't run the heater all that much - no point when the heat just leaks out! So maybe the problem is that it's too cold and damp and needs to be more warm and moist. I gently poked some holes in the soil for aeration, and put a heating pad under the pot to give the soil a bit of warmth. More Florida, less Oakland!
I'm starting to think about how nice a schefflera would look in that same spot, though...