Pumpkin leaves cupping

[idiotwind]

Any idea what this could be? My pumpkin has finally set a fruit that is growing rapidly but over the last day or two several leaves have developed a mottled brown colour in the centre around the veins and they are curling up around the edges. The cupping leaf directly above the squash was green and healthy less than 48 hours ago. Still plenty of healthy leaves but am concerned by rapid progression.
Last few days have been very wet following long dry spell.
Neighbouring courgettes are fine. In a nearby bed some of my spaghetti squash leaves have got some brown patches (albeit they look mostly ok) but the buttnernut looks healthy still.
My first year on the plot and went a bit mad with my cucubits. Planted too many plants too close together and the squash is taking over!

Many thanks,
Ed

[veggiechicken]

Are they old leaves dying off?
I cut off any tired leaves!

[Florence Fennel]

Looks like a bit of powdery mildew to me - cut them off if there are plenty of other healthy leaves