Spots, blotches, or blemishes on the leaves of your plant come from a variety of sources. Intense light causes sunburn on your plant, causing the leaves to blister. Make sure you know what level of sunlight your plant requires to avoid over exposure. Temperatures below 50 degrees F also cause spotting on your plant. Spray from chemicals and over watering are also causes for spots and blemishes. Keeping your plant on a strict watering schedule is an easy way to avoid that problem.