Possibly rootbound, and mites...?

I recommend to transplant into a larger pot of potting soil that contains perlite, copy-paste and fill out the troubleshooting form in my signature, and check the undersides of the leaves with a magnifying glass for mites . (little black dots that move around and suck the juices from the leaves, or chew on 'em or whatever it is they do)

When putting a plant in a pot, try an leave just enough room at the top for watering. The more available fresh air at surface, the happier the beneficials in the soil. (moist and stagnant air is not optimal)