My current situation seems exactly the same as yours. I just do not know what to do. For the last two weeks our 8 mos old chicken has had the same symptoms as yours and we think it is Marek's disease too... paralysis, poor appetite, weak, doesn't want to move. Our vet told us to try come antibiotic which we have given her with moisten wheat bread that she takes well. The medication is complete and she is much stronger now... she can at least stand up and take a few steps, still has an appetite. We just do not know how long we should go though. Is yours better? any suggestions?