Q.jumbo elephant ears
Bought jumbo (not the giant size) elephant ears last spring. They were big then and whenever they would make a new leaf, it was also big. This spring they came up and are not jumbo sized but much smaller. Do I need to fertilize them or do they need to be more mature before they will grow bigger?
Certainly environmental issues may and will effect how the bulbs produce. The cold winter suffered across nearly the entire United States this past winter may have impacted the bulbs. You can apply a slow release fertilizer to the soil.
Did they winter over in the ground or did you store them?
Here are a couple of great articles.
https://www.gardeningknowhow.com/ornamental/bulbs/elephant-ear/storing-elephant-ear-bulbs.htm
https://www.gardeningknowhow.com/ornamental/bulbs/elephant-ear/growing-elephant-ear-plants.htm