Clones can be so suprising! One moment they may look wilty and dying, then you mist them and you can almost WATCH them standing back up... cannabis is a pretty amazing plant.
Ask at your fert shop for an anti-transpirant, which is the technical term for wilt-pruf.
I wonder if you can use neem oil? I neem my plants a lot and they get a nice glossy residue on them which I imagine makes them a bit less prone to wilting, it's just I wonder how much clones can take of the stuff? Hmmm...