diane

Maybe the problem IS overwatering. Check out this post on a non-gardening site about the same sort of problem. ...I thought perhaps I was over-watering them, so I started watering every 2-3 days instead of every day. While the leaves that had already turned yellow have stayed that way, I haven't seen any more leaves starting to yellow at all.

anney, None of the leaves are the slightest bit yellow... they just fall off, green. The only thing that looks even a little unusual about them is how the edges on some are turning a little brown/crispy. But I'll try your suggestion & see what happens. Thanks for responding!

I'm sorry, diane! I assumed the leaves were yellow. (I've been seeing pictures of yellow bean-leaves and just added them to your description!)

But since the edges of the leaves are brown and crispy along with leaf-drop, that can also mean overwatering. See if less water helps. I'll bet it does.