Answer: Unfortunately, the answer is that there are several reasons for this generic symptom on a peace lily. Use the processed of elimination to determine which are likely to apply to your peace lily.
Hard water or softened water have excess minerals that cause brown leaf tips and edges. Switch to filtered, distilled or rainwater.
Using too much fertilizer also adds excess minerals to the soil. If you fertilize, do it only when the plant is growing vigorously and dilute it to half strength.
Allowing the soil to dry to the point that the plant wilts will cause brown leaf tips. Try to water just before the leaves start to wilt.
Keeping the soil constantly wet will cause dark brown tips that spreads to the entire leaf. Allow the soil to dry almost to the wilt point before watering.
I hope this helps you identify the cause of the problem. It's okay to trim off the brown tips and edges. This will make the plant look more attractive and will allow you to determine how to eliminate the cause.
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