More photos for context:

The one on the left is my main concern, although the middle one should be doing better too. I'm amazed at the size I've been able to achieve on the right.

My hardware cloth "basket" ready to bury:

Ben, in the pic with the red circle, those white spots look like crown rot. They’re not mushy are they? The SS on the right looks like it’s growing ok, though it perhaps should be larger. Is your bed full of tree roots like mine are? When my hostas start shrinking, then I know it’s time to dig them up, pull tree roots off and replant. Since you have them dug up, I would try potting the smaller ones until they improve.

I have no voles where I am (luckily) so no experience dealing with them. Does the basket just go above the ground or is under the roots of the hosta as well? If not, won’t the voles just go underneath to get at the plant??

debra

Debra, there were some mushy blobs in there, but I don't think they were connected to the white area.

Tree roots were my first thought, but I didn't find anything excessive. There were some roots, but that's true everywhere in my yard.

I'm hoping the voles won't dig deep enough to go under the screen -- but I don't know if that's really the case.