are you sure they arent getting over watered? It looks the same. Have you tried H2O2 to try to get some more oxygen to the roots? I am of course going to assume pH and everything is within spec. How about water temperature? is there any algae? Root rot? How have ambient temps been? Did you get the 5 wilting clones from the same mother plant as the other 5 that are doing ok?

what type of system?