Answer: Your plant might be suffering from spider mites or from scale insects. Spider mites are very small and are accompanied by very fine webbing along the undersides of the leaves and along the stem. These can be rinsed off with tepid water or sprayed with commercially formulated insecticidal soap per the label directions.
Increasing the humidity around the plant can be very helpful in reducing spider mite populations -- they tend to peak during the winter when the indoor air is heated and so dry.
Scale can be carefully (and tediously) removed with the finger nail and/or sprayed with insecticidal soap or horticultural oil per the label directions. Scale can be difficult to control so it may be worthwhile to isolate that plant while you are trying to treat it.
Always read and follow all of the directions for application of soap or oil and reapply as indicated on the label to achieve control. Cover all portions of the plant from top to bottom when you spray, including the stems and undersides of all the leaves.
I hope this helps!
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