Are you noticing leaf spots with darker rings (see attached) around the edges? this fungal disease is favored by wet foliage. wet springs can contribute to the spread of this disease. some management options such as: variety selection with resistance, foliage fungicide spray (refer to ID-128 for chemical recommendations,http://www.uky.edu/hort/document-list-home-vegetable ) applied as soon as symptoms appear to reduce spread, sanitation, avoiding foliage wetness by elimination overhead irrigation and crop rotation can all help reduce fungal pressure on the plant. if you have any further questions, please don't hesitate to contact me.