I got this plant over the summer and it was doing fine until winter started. Getting the watering amount right had been a challenge. At this point, I've been watering only when I see the leaves start to droop a little (i.e. when the longer leaves touch the edge of the pot, instead of staying upright on their own) I live in Canada and because of indoor heating, it can can get really dry indoors. Humidity got down to as low as 10% for a couple weeks. This is when I noticed the leaf starting to turn brown. It started from the edge of the leaf, moved to the tip, and now the browning is slowly moving downward towards the stem. I've done my best to fix the humidity problem, including misting the plant daily, bringing it into the bathroom when I shower, putting the near the humidifier when I have it on overnight, and turning down the heating in my home slightly. Currently, my apartment is at around 20% humidity for most of the day, but the leaf is continuing to turn brown. I'm not really sure what to do, especially since the other leaves on the plant seem to be in better shape and I don't want to do anything that would hurt the rest of the plant.
Every leaf has some finite lifespan. As long as the leaves that go brown are the eldest, everything is proceeding normally. The lowest on a stalk, or closest to the main stem on a branch are the oldest and should perish before others. Misting is a waste of time, but do it if it makes you feel good because it won't hurt either. Don't worry about the humidity, it will adapt to your environment. Your watering habits are spot on, continue it.
