Brown leaves on a Nepenthes plant can indicate a number of different problems. Here are some common causes of brown leaves and how to solve them:

1. Overwatering: Overwatering can cause Nepenthes leaves to turn brown and wilt. Make sure the soil is well-draining and allow the top inch of soil to dry out before watering again. Reduce watering if necessary.

2. Underwatering: Underwatering can also cause Nepenthes leaves to turn brown and dry out. Make sure the soil is consistently moist, but not waterlogged.

3. Insufficient Humidity: Nepenthes plants require high humidity to thrive. Brown leaves can indicate that the plant is not receiving enough moisture. Increase the humidity around the plant by misting regularly or placing a humidifier nearby.

4. Too much direct sunlight: Nepenthes plants prefer bright, indirect light, and too much direct sunlight can cause the leaves to burn and turn brown. Move the plant to a location with filtered light.

5. Pest infestation: Nepenthes plants can be susceptible to pest infestations, such as spider mites or mealybugs, which can cause leaves to turn brown. Inspect the plant regularly for signs of pests and treat with an appropriate insecticide or soap solution.

6. Fungal or Bacterial Infection: A fungal or bacterial infection can also cause Nepenthes leaves to turn brown. Remove any affected leaves or stems and treat the plant with an appropriate fungicide or bactericide.

In summary, Brown leaves on a Nepenthes plant can indicate overwatering, underwatering, insufficient humidity, too much direct sunlight, pest infestations, or fungal/bacterial infections. Make sure the soil is well-draining and the plant is receiving the appropriate amount of water and humidity. Move the plant to a location with filtered light if necessary. Inspect the plant regularly for signs of pests or disease, and treat promptly if necessary. By addressing these problems, you can help your Nepenthes plant stay healthy and beautiful.