This is my first time growing pole beans. I direct sowed them in May. They looked healthy (though they grew very slowly), but then the leaves started to wilt out of nowhere. Soon after, the leaves curled, got dark green and dry from the bottom up, and eventually developed brown, yellow, and black streaks/spots on them. The photos below show the beginning stages, and the last one (in the purple crate) show the almost-dead leaves I pulled off. Does anyone know what this is? Thanks in advance.