I would consider this to be ich, and Colin seems to be agreeing so that makes me more confident it is ich. There is only one way to deal with this. Increase the water temperature. And do not move the fish to a QT, this is in the main tank and needs to be dealt with there.
I don't know the other species in this tank, but leaving that aside I would increase the temp to close to 90F (32C) for two weeks. As I have posted elsewhere, this species (Parachierodon simulans) naturally occurs in water that is 35C (95F) so this will certainly not harm this species. Depending upon the other species in the tank, I might not go this high, and if so I might use aquarium salt. I would need to know all the fish before deciding.
Do not an any account use any so-called ich remedy with these fish. They will likely be dead before they are better if you do.
With the immediate action covered, for the future: ich is always caused by stress. Healthy fish will not succumb to ich unless they are under fairly severe stress. The pathogen obviously must be present, but it is the stress that causes fish to succumb. And stress can occur from inappropriate water parameters, problem water conditions, too few of the species (initially), inappropriate aquascaping, inappropriate tankmates, using any medications/additives, etc, etc, etc.