Or maybe does it need to be transplanted to a bigger pot?
It could be overwatering. That is common, and it does seem to be the case, here. It could also be rootbound. Both are probably likely. These two articles will offer more information on their care:
https://www.gardeningknowhow.com/houseplants/peace-lily/watering-peace-lilies.htm
https://www.gardeningknowhow.com/houseplants/peace-lily/peace-lily-plants.htm