The same thing has been happening to mine, David. What type have you got? I tend to grow Burpless Tasty Green, which can be grown in the greenhouse or in the garden, but they do best outside. Cucumbers are very greedy feeders, but they also prefer quite a bit of shade, I've found. Perhaps someone will give us some tips! Annie (Cumbria)

I can only tell you about the 3 burpless tasty green cu's I grew in my greenhouse last year.
They grew very well and had a lot of good cu's on them eventually, but only after having a great many small ones at first, so perhaps you're expecting too much too soon.
I kept green shading over the top of the greenhouse all the time they were growing and gave them plenty of water but very Little feed.
I've done exqctly the same this year with a different type and after growing lots of small cu's, some of the top ones started growing quite quickly as did those last year.

Thanks anneashby. Appreciate yr thoughts. I will update as the cucumbers develop...or not.