@kathiemonn
You don't say what part of the country you are in. Dahlias in general don't like really hot weather. But it may just be that they are not acclimatized to lots of direct sun yet. I know that when we have had a week of cloudy rainy weather, and then the sun comes out hard, the leaves get wilty looking, but then they perk right back up when it gets shady again.
If they are not recovering, and looking worse and worse, it may be that the tubers have rotted - but that is unlikely to happen to all of them at once.
