Q.Unhappy Peace Lily
Have a big Peace Lily from a nursery and it has not been happy anywhere I put it. I would water it when the leaves begged for it. I have moved it 3 times as it complained wherever I put it. I repotted it into a larger pot. After so much complaining I decided to re-pot it again for it looked as if it was dying. The center was looking like black tar so I knew it was rotting. I repotted for the second time and threw away one portion of it. I now have two root systems I think and I put it on the front screened porch where it gets filtered morning sun. I thought this plant was happy in dark locations? I fear I overwatered it. But I would wet good when the leaves got droopy. I got this in Feb. and fear I am loosing the battle. I thought this was an easy plant.

Certified GKH Gardening Expert
Black is always a sign of bacterial rot. You will need a fungicide, and then proper care will likely bring it back to health. Usually, wet conditions that stay wet for too long will cause this.
Here are some articles that will help:
https://www.gardeningknowhow.com/garden-how-to/info/using-fungicides-in-garden.htm