Any idea why it's unhappy? Too much sun? Thanks :)

I'm no Spath expert but here are my guesses; I have similar plants.

Too much sun would give it a sunburn on the high spots.
Looks like larger, older leaves are turning. If it ever dries, it may protest by turning its older leaves yellow and killing them off. Lack of fertility can also do that as the older leaves are sacrificed.

I think it is just natural leaf senescence, end of cycle. I see other younger leaves are okay, and it is blooming, overall looks okay to me.

Thanks! Would you trim off the yellow guys? I don't know much about pruning.

I just trim it off once it gets brown, as close to the soil.

Yellow leaves never turn green again, I'm pretty sure.

Sunburn would be more evenly distributed over all the leaves. It is not normal die back of older leaves either nor is it lack of nutrients. Most likely it was allowed to get too dry at some point and perked up after getting water. However, selective leaf yellowing often occurs several days to a week after a drought episode. That said, there is no long term damage to the plant. Trim off the yellow leaves as recommended here and avoid allowing it to reach the wilt point again. Peace lilies don't tolerate dry soil. Also avoid any direct sun rays falling on the leaves. To promote flowers, keep it potbound and fertilize it at half strength monthly.

Thanks for filling us in, Will. It's been my experience with what I think is a Petite spath, to have that drought= yellow event. I was guessing on the other theories I threw in there.

My plants that look similar to this seem thirstier than some other plants, I guess there is a lot of leaf area there.