The copper test kit may read 'none detected' when it comes to copper, but the removal of all copper is important. Make sure you have used carbon and made at least two extremely large (over 80%) water changes. I am assuming they were treated in a quarantine aquarium and that they are still in that aquarium. If either of these are not correct, the fish may be reacting to other stressors. How many were treated at the same time? Were they all together? What size aquarium?
I hope the diagnosis was correct. It just might be there was a secondary problem or that the primary problem was not Marine Ich. Otherwise, the fish do seem to be having issues with something that is aggitating them. Unless this is latent mating behavior (you also don't mention their age or whether or not they are mated), look for any signs of stress.
Without additional information, it could just also be just a phase and they will settle down in a few days.