Monstera Old Leaves Dying. The other reason is that your plant might not be getting enough light. If your soil has gone too dry completely dry the oldest leaves will turn yellow first.
The chemicals within the plant are toxic and can cause skin. Keep a consistent watering schedulewater when the top 2-3 of the soil are dry. If you accidentally let your Monsteras soil dry out completely you may see leaves go limp droop and possibly start to brown.
Be alert to any source of cold drafts which can cause your plant considerable stress and lead to your Monstera leaves drooping.
It is quite normal for plants to shed old leaves that are no longer needed especially as the plant grows bigger and taller. Pruning can also encourage your plant to grow and help you control where it puts out new leaves and in the case of some plants branches. Think of the fiddle-leaf fig. If you accidentally let your Monsteras soil dry out completely you may see leaves go limp droop and possibly start to brown.