Q.Peace Lilly
I have two peace Lilly house plants that are producing new leaves that have no tip or the tip turns black. They both were repotted last summer and are now in a closed office space/ bedroom

Certified GKH Gardening Expert
Are your plants getting much light? Even though peace lilies are touted as low light plants, they do much better with ample light, and they won't bloom without enough light.
Also check whether they are overwatered or underwatered. Hard water deposits also can wreak havoc. Those can be flushed out with lots of water. Try watering with bottled water or distilled water instead of tap.
Here are some care articles that will help:
https://www.gardeningknowhow.com/houseplants/peace-lily/peace-lily-plants.htm
https://www.gardeningknowhow.com/houseplants/peace-lily/peace-lily-leaves-yellow-brown.htm
https://www.gardeningknowhow.com/houseplants/peace-lily/peace-lilies-getting-brown-tips.htm
https://www.gardeningknowhow.com/houseplants/peace-lily/watering-peace-lilies.htm