Be sure the saucer gets emptied soon after watering to prevent this. The plant is not getting enough light. Plants that are highly colored require more light than those that are only variegated with white. The plant may have spider mites. Tap a leaf sharply over a piece of white paper and see if any of the specks that fall begin to crawl away.
Mites strike most often when the air is hot and dry.
Correct those conditions, if possible, to prevent further trouble. Your plant is likely being attacked by aphids. They suck the plant's sap then excrete the honeydew waste. Set the plant in the bathtub and shower it with water to remove the sticky honeydew, then spray it with insecticidal soap to get rid of the aphids. Inc. All rights reserved.