Q.peace lily care
I have 2 peace lilies that aren’t doing so well. I have followed the care instructions that were provided, but nothing seems to be working. I’m attaching a photo so that you can see what is happening. Any suggestions will be helpful. Thank you

Have you repotted the plant to a larger pot in the last year or so?
It may be root bound and not able to take up nutrients for the potting soil and watering.
Also if your watering with softened water or treated water it can build up in the soil and cause the leaves to darken or turn black. It may be first noticeable on the tips of the leaves. You can use rain water or distilled water.
Make sure your watering only when the plant needs it. Check the soil and when the first inch or so of soil is dry you can water.
Here is a link to refresh you on the care requirements.
https://www.gardeningknowhow.com/houseplants/peace-lily/peace-lily-plants.htm