There may not be much of anything that you can do at this point. They could be suffering from a bacterial wilt or anthracnose. Wetter weather can makes it worse. If you have had cucumber beetles in your garden they may have infected your cantaloupe. You will have to wait and see what happens. They may get through it but most likely they will continue to wilt and die. If so I would remove all of the plant material and dispose of it. Here is a link to info about diseases of melons. http://www.extension.umn.edu/garden/diagnose/plant/fruit/melons/leaveswilting.html