Yep, powdery mildew. I got that when I tried to grow bush squash in a shaded location. You can try to pick up some neem oil and spray that on, it helped my lilacs.
One of the squash there might be cucumbers. The other plant.. almost want to say bush beans but the leaves aren't quite right. Maybe a close picture? that one in the back doesn't seem like corn but maybe... or maybe just a decorative plant? And you do have strawberries there.
