The plants are about 3 feet tall and small holes have appeared in the leaves. There does not see to be any insects on the leaves.
What Causes Leaves on Sunflowers to Be Eaten and What Is the Cure
Certified GKH Gardening Expert
There are actually a few pests that like to nibble on sunflowers. Neem oil is generally effective for most insect pests. Here is an article that you may find helpful: https://www.gardeningknowhow.com/ornamental/flowers/sunflower/sunflower-problems.htm