HELP! Chick is acting weird and having seizures!!

I went to check on my chicks just a while ago and they were perfectly fine. Then I heard very loud chirping and walked over to the brooder to see one of my 5 day old buff silkie chick cheeping and moving its head in weird angles. I picked it up and it just kept chirping and looking up and moving its head backwards and to the side and just acting odd like it had a neck injury. I held it up to my neck and it would calm down and stop chirping. All the other chicks are acting perfectly fine and it was until now. It was growing good and acting normal. We separated it from the other chicks and when we put it back in, it rolled on its side and threw its head back and started shaking and had a seizure. We set it up and it stopped and fell asleep. Then it set up and wasn't rolling its head back as much as it was. Then we gave it some drinks of water and put it back. Then it started flipping around and moving its head around. It starts to tremble and then sleeps and then wakes up and flops around, flipping its head back. If it is a neck injury I don't know how it got it unless one of the other chicks stepped on it, I don't see how though because they're all the same age and same breed.We feed them medicated chick started by Manna Pro. Is it just having a seizure or something else?
Here's a video(I know there is a lot of poop but I just cleaned it out):

Also, she is pooping fine(pooped on me twice ).

Just had a really bad seizure and died. I don't know what happened and I don't want this to happen to any of my other chicks, what could have been the cause?

Did you ever find out what happened? I'm sorry that no one responded to your posts. It's really frustrating when that happens. I found it because I have a silkie chick that is doing the exact same thing yours did in the video and between yesterday and today, the seizures are getting worse. Mine is only 4 weeks old and they started just a few days ago.

NCgirl21 said:

Did you ever find out what happened? I'm sorry that no one responded to your posts. It's really frustrating when that happens. I found it because I have a silkie chick that is doing the exact same thing yours did in the video and between yesterday and today, the seizures are getting worse. Mine is only 4 weeks old and they started just a few days ago.

Click to expand...

No I did not. It happened to a older chick of mine, different breed but it has never happened to any of my other chicks since then.