I've had my Ficus lyrata for about four months now and I'm still figuring out the watering rhythm

I've had my Ficus lyrata for about four months now and I'm still figuring out the watering rhythm. It seemed happy at first, but lately some of the lower leaves are turning yellow and dropping. I'm wondering if it's overwatering or just normal leaf turnover? I keep it near a bright window in my tropical climate, which should be ideal. Anyone else deal with this, or am I missing something obvious?