Unless you planted them upside (pointed end should be up, rougher side down) down they'll start to sprout when the soil temp gets warm enough.

That mushy feeling means it's rotted. It should be firm, like a good onion.

The one that is mushy needs to be dug up and the mushy part cut off and the good part needs to be allowed to dry a few days to heal and be replanted. Your soil is not wet is it? They will rot in wet soil.

I just bought an elephant ear plant and put it in water, in a fish pond. Isn't that where they grow? wfike asked if the soil was wet. I live in southern California, and bought a black elephant ear plant. What do I do with it if it doesn't go in the water?