I'm sure it's just because you've been taking such good care of it. Is it possible that your plant is getting too much sunlight? That could explain why its leaves are a little brown. Also, could you check the roots for any signs of rot? If there is any sign of rot, it might be because you've been watering it too much. Third, do you think you could check the leaves for any spots that might be showing signs of pest damage? If you find any, please give it an anti-pest liquid right away.