rabbits get stressed very easily and can die very quickly, I'm sure you did everything you could for him.

I would bring your remaining rabbits inside to keep them away from the mice, mice can carry fleas and mites that could have myxomatosis. give the old hutch a very good clean with jays fluid and leave it to dry before putting another rabbit in it. I would also take the others to the vets for a good check over and if they stop eating even for a few hours rush them straight to the vets.