If you have any plant that has fungus or mildew on the leaf surface, clean the leaves off regularly with a mild dish soap and water solution. Make sure that you place the plant in an area where it has good airflow to keep the surface of the leaves dry. High humidity and surface moisture will be your enemy with this kind of problem. Avoid places like pool rooms, and windows with lots of condensation. Keeping the leaves clean and dry should prevent the problem from re-emerging.