Answer: Peace Lilies thrive best in tropical conditions mimicking their native Columbia. This includes bright light (natural light is preferable to the fluorescent lights) moist soil, high humidity, and temperatures between 75?F-80?F. Peace Lilies also do well with a rest in the winter in cooler temps (between 60?F-65?F) and should be fed every two weeks during their active period. But, they are sensitive to air conditioning so if yours are indoors, that might be the reason for the browning foliage.
Today, many varieties of spathiphyllum are grown. Some are grown for the abundance of flowers they produce. But flowers come at some expense. The cost? Nutrients that go to the flowers do not go to the plant. When plants hold a lot of foliage, they may require more water to support the foliage. You may notice lighter colored leaves and if the plants dry out too much you can get browning tips.
The older leaves are at the bottom. If that is where the brown tips are occurring, the leaves are not "pulling" food the same way, new rapidly growing leaves do. Brown tips and leaf loss in this case may be natural. Aside from watering and relative humidity, and natural leaf loss, I can't think of anything that might affect your plants in this manner.
Best wishes with your peace lilies.
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