Enkyenky's Expensive Redwood Backyard Box garden

I currently have globe squash, yellow crookneck, black plum tomatoes, cherry tomatoes, basil, chards, cukes, peppers, and beets in this little box. It’s nine by four feet and is massively productive. One thing: Some of my squash fruits are rotting on the end, where the flower falls off. I haven’t had this happen before? Any ideas?