I would take the bulbs out of the pots, wash them off and get a good look at them before you spend any more time and effort on them.
If they are soft, or mushy or smell bad, then the rot has gone into the bulbs and they are dead. If you find firm bulbs under the soil with some roots underneath it, you still have a hope.
Did the stem have some healthy leaves before it broke off and turned to mush? If so it may have made a new bulb, which would then be dormant right now.
