Really? Dehydration is actually a noted cause of fallen combs by poultry vets. Usually after they are rehydrated the combs perk back up... maybe I am crazy but my australorps have had this happen in the summer and then their combs are okay again in the winter/spring time.
the marans hens here have leghorn like combs all the time. I do have a cockerel who's comb returns up when he is feeling well but with the hens the reason is genetic.