Beginner Gardening: Help! what is destroying my beautiful zinnias?, 4 by asjd

asjd wrote:
Hello everyone, newbie gardener here, I've planted a flower bed by the walkway in front of my house this spring and at the front of the flower bed I have three zinnias. I live in central Texas (hill country). So the zinnias seemed like a good choice; love full sun and hot weather, are drought resistant, and also bloom frequently.

The only problem: in the last few weeks something has started to eat/destroy/massacre them. Have a look at the photos I'm attaching. I can't for the life of me figure out what it is. All the other plants in the bed are doing perfectly fine, but as you can see, the leaves on these zinnias are being eaten alive.

I assumed it was some kind of pest so I did a bit of research and got just your basic spray from Home Depot and sprayed them. Nothing changed. When I go look at them I can't actually see any live insects or pests, so I have no idea what I'm even dealing with.

Any advice would be greatly appreciated---I'm at my wits' end. Please help me save these beautiful plants!