When did you plant them?
How big are your pumpkins?

If you are in zone 9, you must have planted them in April or early may. So the vines are 4 months old. That is about the life cycle of pumpkins. Of course, hot weather can cause an early end to it too.
Try fertilizing lightly and water more frequently. The younger leaves can stay alive, providing nutrients to your pumpkins. As long as pumpkins are attachec to live branches and their stems are not fully dry, leave them on the vine. After that you can harvest and bstore them on pallets(racks, or something like that) to mature and stay dry.

I planted them in early June (They were a late batch in a new part of the garden). The pumpkins on this plant are a bit larger than a basketball, but the ones on the other plants in the same area are about twice that size (this one set fruit a bit later).

I will try watering a bit more frequently and with some more fertilizer.

Thank you so much for the advice, Cyrus. This is the first pumpkin I have grown that has not been completely taken out by powdery mildew, so I am actually getting to the point where I am encountering some new questions.