They are an all female variety, regularly watered, in a greenhouse with plenty of light. Door and window open every day. Started with lots of small cucumbers and only 3 have fully developed, the rest got no bigger than 2 - 3 inches then shivelled and turned yellow (from the flower end). Any suggestions as to what the problem is please ?
Abortion on cucumbers and other cucurbitaceae is quite common.
This is a way for the plant to regulate its resources and prepare for optimal growth during the season. It might be a fertilizer issue. You may try to limit the growth of the plant by pinching out, to help it concentrate on its fruits.
It could also be a pollination issue, as suggested here by Bamboo. Why did my young cucumbers turn yellow and fall off?