Hi Evanskl
to All Things Plants!
It's difficult to tell from the photo of your
Peace Lily (Spathiphyllum wallisii) It may very well be root bound and just needs a larger container or it could be a soil issue; possibly the soil has become so compacted that the water is running off too quickly and not enough moisture is getting to the roots. I'd remove the plant from it's container and rinse off all of the old soil, cut back any rotted or dead roots and replant in a fresh well-draining potting medium.
