Brown, dry edges on Plumeria leaves can indicate underwatering or low humidity. Ensure the plant receives sufficient water, especially during hot and dry weather. Increase humidity around the plant by misting the foliage regularly or using a humidifier. Adjust the watering schedule to prevent the soil from drying out completely. If the plant is exposed to direct sunlight, consider providing partial shade during the hottest part of the day to reduce water loss through evaporation.