You may wish to ask yourself when the last time was that you repotted your peace lily, and what kind of soil you're using.
They like a rich, loose soil with lots of oranic material (humus, which is compost at the end of it's cycle). They like to be watered and misted, a bit less in the wintertime. Only, you never want to let the soil get dried up.
Repot every year in fresh, new soil that is very good quality. I use Miracle Grow. I hope this is helpful.