Answer: I'm sorry you are having trouble with your plant. This plant needs only low light and should not be overwatered; the soil should be allowed to dry somewhat between waterings. It needs a temperature between about 68 and 80 degrees and needs good air circulation; also avoid wetting the leaves when you water the plant.
It is unfortuately potentially subject to a wide range of pest and disease problems, many of which can cause foliage problems as a symptom. Here is a detailed listing you might find interesting, although they can be somewhat difficult to diagnose.
I would suggest you work with your county extension to determine what is affecting your plant, and based on knowing that, determine how to proceed. If it is something that can be treated, they will know the best method for doing that and if it is something that requires a chemical control they will be able to tell you specifically what to use and how/when is best to apply it.
Good luck with your plant!
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