Maybe there is something wrong with the root system. You can take the plant out, cut off the rotten root system, dry the root system after disinfection, and then replace it with new soil for cultivation. It may also be caused by poor ventilation, so it is necessary to ensure good ventilation, and the maintenance environment should not be too humid, which is easy to happen if the environment is too stuffy.
Plants (angiosperms) include roots, stems, leaves and other growing plants. The meaning is quite different from that of "plant", which is more exact and refers to a wider range.