If you notice brown spots on your Plumeria leaves, there are several possible causes to consider. Sunburn, fungal diseases, or bacterial infections could be the culprit. Look for signs of sunburn like pale or whitish spots, and if necessary, move the plant to a partially shaded area. For diseases, remove infected leaves and apply the appropriate fungicides. To prevent further issues, avoid overhead watering and ensure that the leaves dry quickly. It’s essential to regularly inspect and maintain your Plumeria to manage and prevent any leaf-related problems.