my sprouts have shrunk!!

[Sarah-b]

This is going to sound strange, but my brussell sprout plants which were up to the roof of their pigeon-defence-system stood at around 4 ft and they have now shrunk back by about 6-10 inches! The tops are still intact - albeit a bit nibbled. What could have caused the shrinkage? I think maybe the ground has dropped? Am I sounding insane?

Sb

[Sarah-b]

[Motherwoman]

They may have curled over onto the soil at the bottom end,if you see what I mean!
If they need some extra support either put a cane to them or earth them up to stop them flopping about.