You don't have wilt..wilt is easily recognizable as the leaves and vines start turning black..and yes it happens fairly fast in a couple days...brown leaves at the bottom is commonly called "Barelegs" and is common on some varieties..make sure your clematis are getting enough water..I would prune your pruning group 3 back to about 12" from the soil and fertilize ...Jeanne

Thanks, Jeanne, and also thanks for your responses to my other posts.

My Hagley Hybrid looks the exact same way. We had a sudden hot weekend after weeks of temps below 70* and though I thought I watered enough, I didn't. Happens every darn year. We don't have a nice gradual rise in temps to summer here.