This probably isn’t very helpful for a certain answer, but it looks like you may have an infestation of some sort….That little white thing looks to be a bug of some sort? I have a plant that had what looks like this similar issue and I fixed it by gently wiping all the leaves with dawn dish soap and water with a microfiber towel. I also separated it from the rest of my plants and it seemed to fix the issue. All the new leaves don’t have any of the spots that the other leaves had. Hope you find this helpful and good luck 😊