First off...none of my other chickens have any symptoms. I have one silkie who can not stand, her legs are "floppy" It started out as one leg, now it is both. She is still eating and drinking. It is possible she has eaten some moldy corn, also possible she has a vitamin deficiency. If it were merek's wouldn't my other chickens have it? I have a mix of half-and-half vaccinated chickens, about twenty of them.