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Hi,the leaves on my gold rush courgette have started turning golden(well yellow),it's got a couple of fruit on it,the lower,first leaves are still nice and dark green but the newer ones have turned bright yellow.The new growth is green but has a faint yellow tinge to it.It is between two other courgette vars but these are fine.
  Also a Bon Bon squash,in the vicinity which is currently about six foot long has started turning yellow but only on the growing point,it's still growing strong though and the rest is still green.
  Any ideas what this may be?
  Thanks  :)

Is the yellow mottled? If it is it could be mosaic virus