It's possible she has sour crop if the breath smells. I have never heard of sour crop causing paralysis.
The paralysis/movements in your video makes me think something neurological. Whether it's related to Marek's, vitamin deficiency or possibly head trauma since this is a crested bird, I don't know.
The poop is concerning - looks possibly blood tinged - maybe bacterial infection. A vet can do some testing to confirm this.
Since she is not eating/drinking well and is ill - the crop may not be functioning like it should resulting in sour crop.
Hopefully the others I tagged will take a look and share their thoughts.
http://www.backyardchickens.com/a/impacted-slow-and-sour-crops-prevention-and-treatments
The paralysis/movements in your video makes me think something neurological. Whether it's related to Marek's, vitamin deficiency or possibly head trauma since this is a crested bird, I don't know.
The poop is concerning - looks possibly blood tinged - maybe bacterial infection. A vet can do some testing to confirm this.
Since she is not eating/drinking well and is ill - the crop may not be functioning like it should resulting in sour crop.
Hopefully the others I tagged will take a look and share their thoughts.
http://www.backyardchickens.com/a/impacted-slow-and-sour-crops-prevention-and-treatments
. Did you buy the chicks vaccinated (for Marek's?) or vaccinate them yourself and if so, when? Some people with Marek's in their flock buy in vaccinated chicks and give them a second top up jab when they are a few weeks old. I'm not personally in favour of the vaccine for Marek's as I have read a study which suggested that it may be responsible for the more severe strains of the disease which are now emerging, but that is down to the individual to decide on what is best for their flock in their situation. 
