If the eyes have sticky discharge, the bunny could have conjunctivitis or maybe a scratch to the cornea, and this could be a cause for the lethargy as it would be painful. Which would require rabbit safe antibiotic eye drops and a meloxicam (NSAID) prescription from your rabbit vet, the minimum needed to treat the painful eye condition.
If there's no sticky discharge or a problem with the eyes, I would be concerned that she's contracted the calicivirus that affected your previous rabbits. This can be spread around the environment through transfer, from shoes, from clothes, from hands, anything your infected rabbits came in contact with that you then had contact with, can spread the disease. It would be impossible to completely decontaminate outdoors, so it's more than likely there would be cross contamination and the virus was tracked indoors as well.
Even vaccinated rabbits can be at risk. Particularly if they were only recently vaccinated and their immunity hasn't had the needed time to build up enough to protect them from the virus, and/or if the strain that affected your other rabbits is a different one than is covered by the vaccination these new rabbits received.
I would suggest contacting your knowledgeable rabbit vet right away. If it's an eye infection and caught early enough, it can usually be easily treated with the correct medications. If it isn't an eye infection but something else, the vet will need to properly assess your rabbit. Because of your previous rabbits deaths due to suspected calicivirus, it's very important to make your vet aware of this when you phone them so they can take the necessary precautions when dealing with a potentially infectious disease.
http://rabbitvet.net/AustralianRabbitVets.htm
