Hard to say from a single picture. Investigate with a magnifying glass if you see any insects on the top or bottom of leaves/branches, especially those insects that produce honeydew (honeydew turns leaf surfaces black) like whiteflies, aphids, scale, etc. Spider mites are very tiny, deform leaves, like to chew the leaves... in addition to finding them with a lens, you can detect them by putting white paper under the drip line, shake the plant a little and see if you get dots in the paper that move.
Review standard care issues as well: is it getting more than 6 hours of direct sun? is it getting enough water or too much water? If you insert a finger into the soil to a depth of 4", does the soil feel dry, moist or wet? If you pick soil in between two finger prior to a regular watering and then press the soil, does it form water droplets? Do these tests in several spots, not just one.
