necrotic spots on leaves could be a variety of things. look under the leaves for very small bugs. a preventative neem oil treatment may be in order. make sure that if you do spray them, to use a surfactant, such as yucca extract. also spray at night, NOT while the sun is out or you will burn your plants. This is all assuming that there are bugs on the plant. If no bugs are around, keep an eye on new growth, as it could just be wind damage. If I had to guess from your pics, you might have a small mite problem.
look up organic methods of outdoor pest prevention. just my 2 ¢