Pothos like to have their soil dry out completely between watering. If left continually in damp soil, the roots will rot. Black spots on the leaves and the sudden collapse of the plant indicate the soil has been kept too wet. Let the plant tell you when to water—when it starts to droop, it needs a good drink. However, don’t wait until the leaves start to shrivel or you will lose some leaves. Dry, brown edges mean the plant was kept dry too long.