Answer: Spathiphyllum, or Peace Lily, like many houseplants often suffers from mis-watering. Overwatering results in extended periods of soggy soil followed by root rot and then yellowing and decline of the plant. Underwatering results in wilt often followed by yellowing and loss of some leaves.
Other causes could be cold growing conditions. I would suggest you lean the plant over and remove the pot. Examine the roots. If they are not a healthy, creamy-white color, but rather brown to grey and watersoaked in appearance then root rot has set in. Trim away outer parts of the root ball to remove decaying roots and soil. Then repot in fresh soil and be careful not to overwater. Give the plant a little more light (not direct sun) during its recovery period.
Good luck with your plant
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