Q.Why do I have a yellow leaf on my elephant ear plant
Fort Worth, TX – Why do I have a yellow leaf on my elephant ear plant?

One yellow leaf doesn't usually mean much other than that the leaf got old. Plant leaves get old and worn out, and don't work very well anymore, so the plant pulls out the materials that are in it for use elsewhere, and let's the leaf go. You might want to dig with a shovel to check the soil moisture, it shouldn't be too dry or too mucky. Here's an article on elephant ears that might be useful to you: https://www.gardeningknowhow.com/ornamental/bulbs/elephant-ear/growing-elephant-ear-plants.htm