Answer: The white spots could be sap or it might be a fungal disease or even mealybug or scale insects. Without seeing the plant, I can't really diagnose the problem. Use a magnifying glass to get a better look at the spots. If they are raised and cottony looking, they are probably insects; if they are mostly flat, they could be a disease. Or, take one of the affected leaves to your local cooperative extension office or well staffed nursery. Helpful folks there can identify the problem and suggest control remedies. Best wishes with your plumeria.
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