Cucumber question

For next year I guess!

I have always grown cucumbers quite succesfully, starting in a cold frame and then out by the side of the house once it's warm enough. In some years I have grown them up the garden table as it supports them nicely! But this year their stems were really fragile and kept breaking so the plants died. Only one is still going though I daren't move it from frame as it's stem is also broken but still growing so far.

Is stem breakage down to anything in particular? Food, temperatures? Was I just a bit unlucky this year?