Brown leaves on a Pothos plant can indicate a few different problems, but the most common cause is overwatering or underwatering. Here are some potential causes and solutions:

1. Overwatering: If the soil is constantly wet and the leaves are turning brown and mushy, it's likely that you are overwatering your Pothos. To solve this problem, allow the soil to dry out completely between waterings. Adjust your watering schedule accordingly and consider using a well-draining soil mix.

2. Underwatering: If the leaves are turning brown and crispy, it could be a sign of underwatering. Pothos plants need regular watering, especially during the growing season. To solve this problem, water your Pothos more frequently and ensure that the soil is moist but not waterlogged.

3. Low humidity: Pothos plants prefer a humid environment, and low humidity can cause brown leaves. To solve this problem, mist the leaves with water regularly or place a humidifier near the plant.

4. Too much direct sunlight: If your Pothos is exposed to direct sunlight for long periods, the leaves can become scorched and turn brown. To solve this problem, move your plant to a location with bright, indirect sunlight.

5. Nutrient deficiency: If the leaves are turning yellow or brown and falling off, it could be a sign of nutrient deficiency. To solve this problem, fertilize your Pothos with a balanced, water-soluble fertilizer every two weeks during the growing season.

In summary, brown leaves on a Pothos plant can indicate a range of problems, but most commonly it's due to overwatering or underwatering. Ensure that the plant is receiving the right amount of water, humidity, light, and nutrients. With the right care, your Pothos should recover and thrive.