Seems like you've got fungal infections (mildew and maybe butrytis).
I've heard that stuff like melons, cucumbers and so on aren't very attractive to pollinators, so they can really benefit from hand pollination. I think virginity will be its cause if death :(
The pH range is fine I guess. It being a bit off won't harm the plant catastrophically, it will only make absorption of some nutrients a bit harder.
I wish I could say something more uplifting, but I think it's over. The fungal infection is too advanced, and the blossoms are dead, you can only take that as a lesson and try it again next year.