Lack of trace minerals can cause yellowing of leaves in plants. This isn’t very common, but it happens when the pH of the soil is off.

Bean blight, 5 diseases that cause spots and wilting on beans

Beans are a favorite in the vegetable patch, and not only for us! Many types of sickness-causing fungus and bacteria also love to infect bean plants. They cause brown or yellow spots,wilt, and other issues on bean leaves, bean pods and vines. Here are the main culprits responsible for bean blight.
Types of blight that infect bean leaves, pods and seeds
Any questions? Ask them on the forum!