Are both Cornish X?So vet said it may be Marek's! Another one of our chickens can't walk either. The others seem totally fine. The two unwell ones are inside now, in chicken slings . They're eating and drinking and seem pretty comfortable. Fingers crossed they recover!
Can you post a photo of their legs/feet?
Did you every feel the abdomen for bloat/swelling?
In the photo both of them look wet? Are you bathing them?
While not walking can be Marek's, sadly with a breed like Cornish X leg deformities, ascites and heart/organ problems should also be considered.
The only way to get an official diagnosis of Marek's would be after one has died and further testing/necropsy is performed.