I would not put any birds in with the ones that were sick they will remain carriers for life. They should remain a closed flock.
http://agr.wa.gov/foodanimal/avianhealth/docs/mycoplasmagalliscepticum-website.pdf
http://agr.wa.gov/foodanimal/avianhealth/docs/mycoplasmagalliscepticum-website.pdf
Here's a very interesting thread to read what happened to someone that bought from a swap.
Not sure if you have the same thing but some good advice from a doctor.
https://www.backyardchickens.com/t/69444/sick-dying-chicks-update-8-7-pics-pg-19
So sorry your dealing with this.