Assuming that 30 rectangle tank you mentioned is empty, I would put the Discus in there and do anywhere from 40-90% water changes daily to keep my parameters down. Meanwhile, I would let the other fish cycle the hex tank and hope that most of them live. I only recomend this to try and save your more expensive and delicate discus fishes. There may be a larger issue with your tank and filtration system.
Good luck.
Good luck.