Peace lilies that receive too much water tend to develop wilting, yellow leaves. Stop watering your plant if it has yellow leaves and wet soil. Check that the drainage hole at the bottom of its pot is not blocked. Do not water again until the top inch of its soil is completely dry. Never leave peace lilies standing in a dish of water as this can cause root rot.
If your peace lily's soil dries out completely, the whole plant will wilt and eventually die. Water your peace lily immediately if it is wilting and its soil is dry. Peace lilies sometimes wilt even if their soil is wet if temperatures rise above 80 degrees Fahrenheit.
The fungus Cylindrocladium spathiphylli attacks peace lily roots and causes their lower leaves to yellow and wilt. Severe infections kill all the roots and the whole plant. Discard any peace lily that you suspect is infected by Cylindrocladium spathiphylli and remove any other peace lilies from the vicinity. Treat them with a preventive does of a soil drench containing thiophanate methyl.
Temperatures above 90 degrees Fahrenheit or direct sunshine cause peace lily leaves to fade and develop dead margins and tips. Move your plant to a cooler location and out of the sun. Temperatures below 60 degrees Fahrenheit will also damage peace lily leaves.