The leaves and stems should continue to grow after flowering. Cut back the yellow leaves water water water really well. After new growth starts give the some fertilizer. You should get a second flowering out of them. And then again sometimes they just don't like the heat but you could help them out by shading them and keeping the well watered.

i have planted calla's in my garden, are the bulbs suppose to be pulled out every fall. I live in Ontario, Canada.