Courgette & Cucumber withering

I have a roof terrace garden with lots of pots of both ornamental and edible plants. But can anyone help me figure out what is happening to my cucumber and courgette plants? The leaves are just going crinklier and crinklier until the plants simply give up the ghost. I've sprayed for aphids, the soil is damp but not waterlogged, the stems are firm and healthy looking but every time they get to about 10 inches /25 cms high they start to struggle. I've put some in the shade, some in the sun, I've added fertilizer to some and not to others.

I had the same thing happen from a Spring sowing so I thought I might have more luck with an Autumn sowing, but I appear to be going down the same road. Having just moved here from the UK this year I always knew that the first year was going to be experimental but I'm perplexed! The nearby fields around Palomares are growing squashes for fun...I think they're doing it for spite. 🤷🏽‍♂️

If anyone can shed any light on what I might be doing/not doing I will be very very grateful.

Jimbo 😎