Thanks so much for your thoughtful note. It has been very happy until recently.
I water it in the pot, then check underneath the next day to make sure it's not sitting in water. There was a bit of water underneath when I checked last so I emptied it out. Usually it soaks it right up.
I have never fed it. I know I should. It's winter now though, and everywhere I've read says not to feed during the winter months. Should I wait until spring?
That's an interesting idea about tap water salts. Perhaps I'll carry it outside and use the hose to give it a good soak and see what happens.
Another thought I had: I wonder if it's outgrown the pot. But that wouldn't necessarily cause the leaf issue. I should also mention that I've noticed some very small thin red root-like tendrils trying to extend over the edge of the pot. That makes me think it's thirsty...?
Thank you again, and let me know if you or anyone has additional ideas or advice.