I'm very sad to say that Neville had to be put down yesterday. What we thought was ear mites turned out to be something more serious, and he started diplaying severe neurological systems, so he had to be euthanized.
It's such a shame - he was such nice boy, so fun and active and affectionate. But there was nothing to be done; now we can only hope whatever it was doesn't affect the remaining three rabbits.
Rest in peace, Neville.