My peace lily leaves are all brown on the edges.
Drought stress is usually the cause of this problem with peace lilies (Spathiphyllum). Keep the soil slightly moist to prevent wilting and browning. Peace lilies will let you know by their drooping leaves that you waited too long to water. They usually recover but at some point the plants start permanently wilting and the leaf margins start to brown. Try to water just before the leaves wilt. Over watering causes the same problem. Adjust your watering schedule to fit the growing conditions. Water thoroughly and often enough to keep the top several inches of the soil moist but not wet.