Prevention is Key
Fungal issues thrive in damp, stagnant conditions. Good air circulation and proper watering are the best ways to prevent them. Avoid letting water sit on leaves for long periods, and water the soil, not the plant.
Treatment
For issues like powdery mildew, you can treat them by wiping the leaves with a solution of neem oil or a mild fungicide. For root rot (caused by overwatering), you'll need to remove the plant from its pot, trim away any black, mushy roots, and repot in fresh, well-draining soil.
