A light green color can indicate lack of nitrogen. If they are stunted, it could indicate damage from herbicide. The leaves will be smaller, deformed, and often fasciated. If it is herbicide, the plants would be in areas where there was treatment. If they are randomly placed in the garden, then you can rule out herbicide. Another possibility is virus, though it would not affect a broad number of plants. Viruses can cause deformation of both the flowers and foliage. At this point in the season, there really is not much to do. The annuals will die with frost and the perennials will die back to the ground. If if it is nutritional, making sure there is regular feeding through the growing season will help.
