Its hard to say definitively from this photo, but we think there are maybe two issues; one looks like sap-sucking scale insects (the little brown/tan bumps on the leaves), but it also looks like you may have spider mites – they are very tiny and we cannot actually see them in the photo, and you will need to use a magnifying lens to rule them in or out as part of the problem. We also see “hard water” spots or some other residue on the leaves, so maybe what appears to be spider mite feeding damage is caused by one/both of those. Scale insects will not usually kill a plant, but you will want to control them so they don’t get too numerous. They excrete a sweet, sticky “honeydew” that attracts ants and sooty mold fungus. You can control them by wiping them off with a moist cloth, or cotton swab, or you can use a pesticial soap or horticulural oil product. We recommend wiping off by hand (from leaves and stems) in any case, and before spraying a chemical product to help control the nearly invisible tiny crawler stages of these scale insects. The lumpy ones are the reproducing females that have stuck themselves to the leaves and are building a covering over themselves. Here’s a couple links with more info about scales and spider mites:
http://www.ipm.ucdavis.edu/QT/spidermitescard.html
http://www.ipm.ucdavis.edu/PMG/PESTNOTES/pn7408.html#SOME
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