This plant has growing like crazy, since I got it. I think 3 fully grown new leaves in the time I've had it. There's even a tiny little baby growing at the bottom. Suddenly, two of the mature leaves turned brown and drooped, and when I touched it to inspect, it came right off. Some of the mature leaves now have some spots/browning as well. The soil is damp, and I only water it when it dries out, which I've been doing for a while now and the plant has been super happy until now. Any advice? Thanks!