Bjw13. I just got an order this week from a hatchery and am having the same problem. Out of 16, we had two dead on arrival, and three on their way out. After 24 hours, one of the dying ones is still with is, and I have no idea what to do. She is chirping, but basically has no control over her body. She is rolling backwards and on her side. Wont eat, but we help her with water. She also was vaccinated for Mareks. What did you end up doing? Can they get mareks from the vaccine? Is this what it is, or just shipping stress?
I put up links to tons of info, in the above posts. There is no way to know if it is mareks, without a necropsy ( which can be done by your local extension for less than a vet, or your vet )...No, they can NOT get mareks from the vaccine, the vaccine is a modified live turkey version of mareks...but they have NOT built immunities to mareks until 14 to 21 weeks after vaccination, atleast, and with so many chicks being shipped across the country by the post office, it is possible for chicks to come in contact with it, as it is literally everywhere...it is also possible to have it in your flock already and not even know it...there is NO cure for mareks!!! Also, birds that DO reocover, become carriers for life!
The vaccine does NOT stop the chicks/chickens from getting mareks! It only stops the tumors from forming and helps the chicks build an immunity to mareks, so if they do come in contact with it, they have a better chance of surviving it! But it takes time for the vaccine to help them build the immunities, just like when you have your kids immunized.
I never had mareks in any of my flocks...but the links I put up, are from OP's that currently are dealing with it in their flocks...I would highly recommend reading the links...the description for mareks is the baseline for symptoms, but if you read the thread also, links provided above, you will read other symptoms also...please refer to those links as they are the professionals!!! This is how I am learning!!! First link is the description, second the thread with OP's, prefessionals, talking about how they got it, what they are doing, ect...best to read from them!!!
Best of luck !!! and sorry I have no definative answers for you!