It's been pretty dry out, have you watered them? My hostas get some sun, but not that much. But it has been especially hot, dry and sunny for the past few weeks. I would try to water them and see if that helps.

That's what I thought at first, so I've been careful about making sure they get watered every 3-4 days a good deep watering. But I'm worried about too much water...I've always been under the impression that hostas like to drain pretty dry before the next watering?

I have quite a few varieties of hostas and they do well in heavy clay soil that almost never dried out. Most of the variegated types can take at least 2-3 hours of sun. I suspect that they may have dried out. You may want to replant them in the same spot and make sure that the roots are in good contact with the surounding soil and water well.
Some large blue and blue green hostas can't take as much sun,