Problem with putting 6 week old chick back with its flock

[Our6chicks]

I recently had to separate one of my Bielefelder chicks from her sisters because of respiratory issue. After two weeks of being separated, she was well and ready to go back in with her sisters. (1 Rhodebar, 1 Bielefelder , 2 55 Flowery Hen, 2 Cream Legbars). (They are all 6.5 weeks old). The two 55 Flowery Hens started pecking at and chasing her. Being little witches. All others are fine. I put the two witches in timeout in separate cage but next to the other.
Question: How long should I keep the witches in timeout?!

 

[LaFemmeKatia]

Try a day, and see how it goes. If the Mean Girls are still bullying, put them in time-out another day.
Make sure they can all see each other.

 

[Our6chicks]

Try a day, and see how it goes. If the Mean Girls are still bullying, put them in time-out another day.
Make sure they can all see each other.

Thank you! I do have their cage right next to the other so all can see each other. Mean girls are not happy. Lol. Serves them right.

 

[Pghelp]

Maybe try adding one mean girl at a time? Or even taking turns doing that. They don't like being alone and that might cure it.