If rain has recently hit your garden, it could be a leaf blight. Or if you have bush beans and they have already given you a harvest, they could just be done for the year. In either case, harvest what you can and pull up the plants if you see mold or brown on the foliage. To prevent leaf blight, never work, weed, or disturb bean plants when the foliage is wet. Warm weather and wet leaves is a perfect environment for fungus among us. Keep growing, Marianne Binetti