Cut off the dead flower stalk/s & allow the foliage to gradually die down. Then store the bulbs in their pots on their sides say under the greenhouse staging until next Autumn when repot into fresh compost & water to resume growth. This works in UK & better if greenhouse is frost-free, otherwise a cool, spare bedroom would be just as good.
It seems a bit early for them to have finished flowering, but I suppose it depends on when they were started off.
I know I kept one going for several yrs this way until some type of wasp decided to lay eggs in it over the summer- ugh- when the next generation started to emerge, J.