I suspect the other 2 of her breed may have picked on her. Most of her feathers are gone. No blood but her pink skin shows. Should I separate her from the others? What can I do to help her thrive?
She seems ok in other areas.
If you believe the others are picking on her, then you may need to separate her out. However, that causes problems as when you re-introduce her, she will again be at the low end of the pecking order and it will all start again.
I'm not convinced it is picking yet....juvenile birds grow feathers at odd rates and the down can drop out before the feathers come in leaving naturally bare spots.
I'd watch over the next couple of days to see if she is being unduly hazed. If so, you can set up hiding places for her, or remove her.
Also make sure there are separate feeding stations and that all birds have adequate protein and adequate space. That can reduce picking. Also make sure you don't have too much lighting. That can cause picking.