Notes on my Peace Lily

My peace lily (Spathiphyllum wallisii) has been dropping leaves like crazy, and I'm still not sure if it's underwatering or just needs a bigger pot. I've had it for about six months and it seemed fine until last month. Does anyone else find these things finicky about humidity, or am I just overthinking it? I moved it away from the heating vent, so fingers crossed that helps. Would love to hear what's worked for others.