Leaves have brown spots new leaves ok for a while them get same is it the soil
Certified GKH Gardening Expert
More than likely, yes. More specifically the soil is either too nutrient rich, or has a fungal/bacterial infection. I would add a little wettable sulfur to the soil to kill any infection, or prevent it if the soil isn't infected.
These don't need feeding often. Especially if there is already slow release fertilizer in the soil. Also, make sure not to over water the plant. This could cause fungal infection. Water when the first two inches of top soil is dry.
Here is an article for more information: https://www.gardeningknowhow.com/houseplants/peace-lily/diseases-spathiphyllum-tips-treating-peace-lily-diseases.htm