Strongly depends on individuals, but sometimes it rots suddenly just after the end of summer. The base of the foliage becomes unusually soft, so it is recognized by touching it. There are 3 examples I found: 1)A plant in good condition suddenly rots just after the summer, 2)A plant decreases its size every summer and finally it rots. 3)A plant blooms just before summer or in summer, and it rots after blooming because of consuming its energy. Once it starts to rot, rotting part spreads out by putrefactive bacteria. In some cases, plants are sold in half rotted ondition. Check the base of the foliage, not only leaves. When the growing tip rots, it can be recovered by removing rotting part as shown in the photograph. As introduced everywhere, plants coming from high altitude area tend to be weak in hot and humid condition. Also the weakness strongly depends on individuals. Sometimes it grows well unexpectedly by cultivating hardy individual. The critical solution is to prepare windy condition in hot days by using fan, for example. But it costs much. In this site, their behaviors were recorded in the room which is closed up even in hot summer days. So please refer which species are weak or not.