Courgette plant: disease, nutrient deficiency or neurosis? (With pictures)

[Bramble_killer]

I take back my comments and you should follow womble's and zaz's advice

[ddiogyn]

Thanks everybody.

I think i'm going to have to write this individual off; the three affected leaves are now completely dessicated, and a fourth is beginning to turn. I'll continue treating it as usual, but i won't hold my breath! Fortunately i have half a dozen more that seem to be doing much better