Courgette Leaf Problem

Is this blackening on these courgette leaves from the drop in temperature over the last week or something more serious please? It started last weekend on one leaf and now three are affected. It is on its own at the end of a vegtrug and was the first to go in as a small plant, not direct sown. It has a flower that has been open for three days and seems to be doing okay, with others lower down not yet open.



The other two at the other end of the Vegtrug are fine, but went out about three weeks after the first one.



Thanks, Tink.

 

My personal thoughts are that it's got a virus.
The new leaves look distorted.
Second plant looks ok,I'd get that bad one out of there.

 

Unless of course it's been frosted, have you had any frost since it's been there.

 

@pete there was a whitening on the shed roofs on Monday morning and cold with almost constant rain for two days, strong north winds also. Then yesterday afternoon sunshine and warmer temps, okay today also. I have cut the three blackened leaves off, I’ll check it again in the morning and if more have appeared I’ll pull it out as you advised.

Thanks for your help, as always