This is most likely botulism. All three rabbits are showing similar signs and symptoms, with rapid onset. There is no genetic relation, and limited potential for contagion by virus.
The progression and recovery profile for Ruby is perfect match for botulism. In light of current information, botulism seems most likely; though given the tissue autolysis in the pathology of the dead rabbit trichothecene mycotoxin can not be completely ruled out.
