If kept at 18/6 they will re-veg, but it may take as long as 4-8 weeks more.
From my experiences, it seems if they develop small branches down low, topping them and removing the weird flowering section will lead to faster growing cuttings of/with normal vegetative growth.
Otherwise, just keep them at 18/6 and they will eventually revert to veg again, but it will take a lot of patience and may not be worth it, unless the cuttings are of a special interest plant, the last seed of a particular strain, or are from a "super" mother plant with exceptional performance.
Hope this helps,.........
Organoman.