I can see the good idea of separating it for treatment so that it'll be healthy before it's returned to its flock. For me, it's a debate. In my past experiences with my birds (quail), when I've separated a bird from the flock/covey for a few days due to aggression (the bird was in a cage and all of its group members could see it), the bird is not welcomed very well and is treated somewhat roughly when it was returned back. The covey would gang up on it for a bit but not to any extreme though. They sure do have poor memory remembering their own member. So for me, the good = the bird is showing less/no aggression compared to when it was with the group, the bad = it's rejected from the group. I usually have to weigh the options. If it was a case where the bird would end up dead if I didn't treat it, then yes I would separate it. But my cases were somewhat miner and so I've resorted to treating the whole covey instead of separation. Though my case was for aggressive reasons, I wouldn't expect anything different than if I were actually treating it. I haven't raised chickens for some time so it may be different for them. Just something for you to take into consideration.
