[cc]

Although I am getting cucumbers off the plants lots are dieing at the flowering stage. Plus the leaves have gone yellow. They started doing this ages ago. I would have expected to have an excess of cucumber based on amount of flowers. I am pretty certain they have been watered sufficiently. I have been away for 2 weeks and there is only one cucumber on there?

[Aunt Sally]

Have you been feeding them?  Intervein chlorosis Is a sign of magnesium deficiency.

Have you checked them for red spider mite ?

[mumofstig]

Have they been fed and watered while you were away? They're greedy plants and need a lot of feed and water and root-space to do well.

Snap Aunty 

[Mr Dog]

Mine went like that a while ago after suffering a massive infestation of 'thrips'. They also decimated my dwarf fine beans and had a good go at my indoor 'large' carrots, although I think I may have managed to save them through spraying - the proof will be when I pull them in the next month or so.

[cc]

Have you been feeding them?  Intervein chlorosis Is a sign of magnesium deficiency.

Have you checked them for red spider mite ?

Noticed spider webs on them? But didn't look for spiders. Is this what happens when you get re spider mites?

[Mr Dog]

Have you been feeding them?  Intervein chlorosis Is a sign of magnesium deficiency.

Have you checked them for red spider mite ?

Noticed spider webs on them? But didn't look for spiders. Is this what happens when you get re spider mites?

Sounds like spider mites. https://leafyplace.com/spider-mites/