Overwatered lilies will start dying because of root rot, which is a fungal disease that can destroy your plants.
The best tip I can give you is to always check the soil’s moisture. How?
Stick your finger in the soil and see if the top few inches of the soil have dried out – if so, it is time for watering. If the soil still feels moist, postpone watering for a couple of days.
Pay attention to the plant’s cues. If the leaves start to droop, it may be a sign of underwatering, while yellowing or wilting leaves could indicate overwatering.
If you keep your plant in a warm location with direct sunlight, the soil will dry out quicker.
On the other hand, if you keep it somewhere dark and humid, then it probably won’t need as much watering.
Your peace lily might be turning black if the humidity levels are too low. In this case, you can frequently mist the plant or group your houseplants together to create a microclimate.