I'm glad to hear she is a little better. It is good that she was vaccinated for Mareks. Sometimes vaccines do fail--some say as much as 10% of the time with Mareks. Also, if someone has had Mareks in their flock, then vaccinates chicks, those chicks must be kept isolated from any contaminated area for 1-2 weeks while developing immunity. I am so hoping it is just a vitamin issue--they are pretty common in chicks.