I am really sorry
I think taking your remaining Rabbits to the Vet for a check up
today is pretty essential. Coccidiosis is one possible cause of the two tragic losses and this would put all in contact Rabbits at risk
So a PM of poor wee Smartie is pretty essential too.
http://forums.rabbitrehome.org.uk/s...sis-All-Rabbit-Owners-Should-be-Aware-of-This
In the meantime I'd do a thorough clean of the environment, removing every microscopic trace of fecal matter. Then a thorough total disinfection of the entire accommodation followed by a steam clean. You may need to house the remaining Rabbits elsewhere while everything dries out.
I really am so very sorry