bullied or sick platy?

[Wired76]

I've had some problems for a while with my female red-wag platy. She hasn't looked healthy for a few weeks: she's lost a lot of weight and her fins have been routinely clamped. I thought I was going to lose her after she didn't surface for food for two days, but then she stated doing so again and seemed much better. I just came home from a few days of vacation, and I noticed she's lost even more weight and seems to be missing scales. (I'm attaching a photo.) I'm pretty sure it's bullying, because everyone else is thriving and my water parameters are fine. Originally she was in the (10 gallon) tank with just another female platy, but when he wound up becoming a male platy I got two additional female platys a few weeks ago. But, I think one of the new female platys is actually the bully. I don't have a quarantine tank, but I do have a breeder box. Should I put her in there for a few days to give her a break? I'd like to make her stronger again before she interacts with the other fish, who I feel like have clearly identified her as the weak one. Also, if I've misdiagnosed, let me know. Any suggestions would be welcome.

 

[Delapool]

That's an unhappy fish I'm afraid. Not sure if there is a kink in the body?

I can see some ruffled scales near dorsal fin and looks underweight.

Would try to seperate. As no QT would go for a dark breeder net or box but should be decent size and you don't want fish to be able to peck at it when lying on net or box base (double net or something).