Certified GKH Gardening Expert
There are a few things that can cause this. The first maybe that the plant is underwatered. The second could be a fungus on the leaves. The third could be root rot, which is commonly caused by overwatering, but can also be caused by a fungus.
I would check that you are watering correctly for the plant you own and also treat the leaves and soil with a fungicide. That will cover all your bases.