Oh that fallen leaf, maybe a sign of rotting..either crown or collar rot..either way, just be ready if the remaining leaf falls too. Throw out that other fallen leaf..anything like that, consider it infected.
It may still also try to make a basal keiki..but it does not always happen. So if you still intend to care for it, repot into a smaller container and with a chunkier mix. It will require all your patience. Good luck.
