2 chickens down, Mareks?

I'm not sure what is going on with this new little flock, at this point I'm leaning towards Mareks :-( ....?

Chicks hatched Nov 26. I kept them inside until December 27th when I moved them to my outdoor coop. I didn't have any other chickens in there, I had passed on my old girls that weren't laying anymore, to a friend. Dec 31, we were out of town and my friend calls and says that one chick looks like it broke it's legs, as it can't walk. This chick is unable to walk, legs splay out backwards, not forward and not one forward and one backward. Chick is eating, drinking and pooping fine. I have it in a laundry basket in the garage. It's still there. I went to the feed store yesterday and they said maybe it got splay leg from walking on a slippery surface (shavings). I hadn't let them out into the run yet, when it fell ill.

Fast forward to today, 9 days later, I have another chicken down. It's doing the same thing as the first one. I noticed it limping last night and this morning it's just laying on the coop floor. I have electrolytes and vitamins in their water, chicks are on medicated feed. They were not vaccinated for Mareks. I kept thinking it was a fluke thing with the first one, but now a second. I'm devastated and not sure what to do.

Splayed legs is something newly hatched chicks can develop due to loose ligaments and slick flooring. It's not something that birds more than a few days old are prone to.
Where your previous birds vaccinated for Mareks?

The previous birds weren't vaccinated for Mareks. Could they have been carriers without being sick? I hatched them in my incubator.

Have you been in contact with anyone else's flock?

No contact with another flock. No one in my suburban neighborhood has chickens but us.

So probably not Mareks. Usually infection is bird to bird or humans with poor biosecurity. Could be nutritional. What are you feeding?

Nutrena 18% medicated chick starter grower.

Have they gotten into anything possibly rancid, or rotting? Botulism is another, less common cause for paralysis.

Not that I can think of. They were completely enclosed in the garage until I moved them outside. Then they were in an enclosed coop. I bought new shavings and a new bag of feed last night. I'm going to completely clean anything, and use new feed and shavings in the coop. I bought vitamins and electrolytes yesterday, that I put in their water.

try vitamin B12 oral syringe. Sometimes helps with neuro symptoms.