I suspect you are overwatering the beans, which WILL make the leaves turn yellow. Eventually the plants will die. Water only when the soil is dry two knuckles deep, and then deep-water the plants. Let the soil tell you when to water -- the beans don't need a watering schedule. Don't fuss too much with them, just keep them weeded, and they ought to do just fine.

Have they been under any stress...I will tell you that I don't believe yellow leaves means disease necessarily...I just go along and snap the leaves off so they don't bother me....and unless I see something other than the occasional leaf or the look of real disease, I don't worry about it...plants just do that sort of thing from time to time for whatever reason..to much water, too much heat, rough handling ...whatever..

Hi Charlie I think you've probably got a few problems going on - phosphorus deficiency is highly likely and there is a possibility you have a few other more minor deficiencies as well. If you check out this page about diagnosing nutrient deficiencies you will be able to get some more information to help you diagnose the issues. The deficiency/ies may be due to a lack of nutrients in the soil but excess water and cold soil will also affect the ability of your plants to take up nutrients. My guess from the information that you have given is that a combination of these things is causing your issues. The above website has a page for each nutrient that describes in more detail the symptoms of nutrient deficiencies (and toxicities) as well as methods for treating the imbalances - including if you need to warm the soil, investigate other toxicities or deficiencies (as these can induce other nutrient imbalances) or reduce watering. As an example, this page describes the symptoms of phosphorus deficiency and how to treat phosphorus deficiency. You may also be interested in this blog post about someone purchasing new soil that was phosphorus deficient. Unfortunately, purchased soil can have as many problems as existing soil sometimes! Luckily there is a lot you can do to remediate your soil. I hope that helps but please feel free to ask any questions you may have.

I agree it is not worth the effort, just plant more beans, there is still time for bush beans unless you are far to the North. I'm planting a few last minute sowings this weekend. They don't transplant well.