Burning of the leaf margins is usually from excessive fertilizer. Soil problems such as compaction and poor drainage can severely stunt plants. Soil compaction, poor drainage, etc. Pesticide injury is usually uniform in the are or shows definite patterns. Insecticides cause burning or stunting.
Herbicides cause burning or abnormal growth.
Ozone levels may rise as hot, humid weather settles in for long stretches. Look for irregularly shaped spots which may look similar to feeding of mites and certain leafhoppers. Ozone flecks are usually concentrated in specific areas of the leaf, while feeding damage from insects is spread uniformly across the leaf.