Cucumber dieing on the vine

Can't remember which these are but meant to be small cucumbers. I have had 3 perfect ones of them. But just noticed the rest are not developing? Just dieing on the vine? Any ideas?

Outdoor cukes won't have been enjoying the recent cool, wet, and windy weather at all, and if they're a 'ridge' type which needs pollinating to set fruit there probably haven't been many bees about lately to do that (flowers which appear to set but then abort the fruit is almost always due to lack of pollination.)

Not much you can do except hope for better weather, unless you're prepared to have a go at manual pollination using a cheap artists' paintbrush or similar.

What variety are they?

Looks like an all-female variety, so not a pollination issue.

My all-female GH cukes (la Diva this year) tend to abort new fruits when there are several other maturing fruits on the vines, but also easily run out of steam anyway

Normally, flowering/fruiting plants are fed with tomato food at this stage, but John recommends a high nitrogen feed given the need to keep them growing strongly.
I tried that last year and it seemed to kick-start them back into action.

Looks like an all-female variety, so not a pollination issue.

My all-female GH cukes (la Diva this year) tend to abort new fruits when there are several other maturing fruits on the vines, but also easily run out of steam anyway

Normally, flowering/fruiting plants are fed with tomato food at this stage, but John recommends a high nitrogen feed given the need to keep them growing strongly.
I tried that last year and it seemed to kick-start them back into action.

Comfey feed?

A general purpose liquid feed would be better as they tend to be higher in nitrogen (e.g. Phostrogen or Miracle Grow) but any feed would be better than nothing, especially if you've not fed them at all yet.

As to saving seeds - that's a bit hit and miss, especially if you're not 100% sure of the variety - the seeds may not come true to type next year, and may not even be viable.

I am sure of variety as I have the label.