I've been having this problem all year, but most of my kentucky Blue green beans only plump a few of the lower beans. The tops are almost always thin. I notice that when the weather is cooler I get better beans so it's definately a heat problem. But if so, then why am I getting half pollination and always on the lower part instead of dropping the beans? Does good pollen always get distributed to the lower portion first? I'm wondering if this has something to do with the variety. Any ideas?