I just read that caladium tubers take 3-4 weeks before they sprout. It all depends on the soil temperature, which should be 70 . So, give it just a little more time.

You should give them at least some water.

Yes, water

Maybe it should be, water once, and then don't water again until you see the sprouts. That just seems contrary to all planting that I've read about, to not water at all :-)