Well they have been isolated since hatch and have been down in the basement. I have my little girl in her own brooder with a heating pad underneath the brooder and she is in a donut shaped towel to keep her from falling over. I think she is having some kind of seizure once in a while. I noticed it 3 times so far, once while she was just sitting still and twice while I was feeding her and giving her water. It looks like she is pecking, but when she was drinking it was so strong she almost put her whole face in the water. Thinking back, during and after I took off the rubberband for her splayed leg, she was doing a lot of walking backwards. Like she was dizzy or off balance. So maybe she just wasn't right at hatch, but I didn't notice because of the splayed leg. She did get trampled and jumped on by her 2 siblings, before, during and after the splayed leg issue. But no matter what, those chicks will be in isolation for another month at least. The more I read and think about it, the less I think its Marecks, but still watching just in case.
Since you have some very precious chicken, I would recommend that in the interest of their well being as well as for your peace of mind, you should have her put down and get a necropsy done. If you don't know of a vet that does that, I can get you couple of contacts. With the precious breeds you have, it will be well worth the expense.