Wierd Cucumber problem

[Norm]

OK Grapes, spit the bones out of this one!
8 x 6 greenhouse, floor dug out 4", plastic lined and gravel filled.
8 growbags compressed to two thirds long. 2 plants in each growbag.
There are 6 Toms, 3 sweet pepper. 5 chili plants and a grape vine (in a BIG tub), all doing well and 2 cucumber plants. Now here's the rub.
One cuc seems to be growing and producing fruit nicely all the way up it's 3 feet of growth. However, in the same growbag, the other cuc produces fruit which get to 2" and then start to shrivel and go yellow/brown. Not just at the end like with black rot, but the whole length and they remain straight!
Growbag is level, compost is moist from top to bottom, not wet, bag has drainage. The stem/leaves are healthy, no stem damage. The house floor is kept moist and they get fed every 2 weeks. Ventilation is OK, Max/Min thermo reads 27/12c.
Any ideas?

[Norm]

Dear all, repeat after me, Norm, you're a plank!!! I think I've worked it out. When cuc's don't get enough water for masses of fruit, they do a Star Trek and shut down life support on non-vital systems. I hadn't pinched out the side shoots to two fruit per shoot, so when the higher shoots got to 3 or 4, the plant dumped the lower fruit. I think I've got it sorted now. Thanks for listening.

[JennieAtkinson]

Great you've sussed it out Norm!

[Matt.]

Thanks for this albeit answering your own question. I suffered this cucumber problem last year but it appeared to be quite sporadic. I assumed it was the plant rejecting the fruit due to a problem. However I did keep getting some sucessful fruit and thinking back it did improve after I cut back a lot of the plant because it was swamping my tomatoes! I would never had guessed it was because the plant was too big for its environment. It can be crazy this growing lark!