Oh, I hope notI hate to say it, but this is most likely MG. I dealt with MS a few months ago in chicks that I picked up from a local breeder. The good news is that you don't have to give up on your other flock yet! There is the possibility that your other birds aren't sick! We ended up culling the sick chicks. It saved our established flock. Here is the link if you want to see the detailed process we went through.
Sorry about the MS.
I wish. I’m afraid that all my birds have been exposed by now.
Thank you for the link. I’ll check it out if I find time.