It sounds like a simple infection. I had a similar problem with my money plant and I solved it with the following actions. You can try repotting it into a larger pot with sterile potting soil. Water with a mild fertilizer when the top of the soil feels dry. I would also give the leaves a bath with lukewarm water and mild soap. After that, lightly mist the plant daily with distilled water. It is likely that you might lose a few move leaf clumps, but it should probably improve within a couple weeks.