Something is Eating My Dusty Miller at the Roots?

I planted several Dusty Miller plants approximately 3 weeks ago. They were looking very healthy and growing nicely until a few days ago I noticed that 1 of them was severely wilted. I knew it wasn't from lack of or too much water because the others (12 more) looked great. Then a day or 2 ago I noticed 2 more doing the same thing. Not next to each other but randomly. They don't die quickly they just wilt.

I immediately assumed that something is eating the roots. When I pulled up the first one several sow bugs came out. I know that sow bugs will eat on decaying material. Then I pulled up another, not so progressed one, and a couple of sow bugs. I'm not seeing anything else in the soil. Before I planted I tilled the soil. I didn't see any grubs.
Any suggestions?

By Mark