I know this question was asked three years ago but I'm glad it was
The responses have set my mind at rest.
My big, beautiful English buck, Ollie, died very, very suddenly two weeks ago. There was nothing wrong with him but shortly after a brief thunderstorm he hopped out from under my desk, stopped, hunched up and no more than two minutes later had died! He was only two and a half
He'd been to the vet to hold his flatmate's hand because she needed to go, so the vet had seen him and knew Ollie was fine. When we spoke to him later, he said it was "bizarre" and could no more understand why Ollie had died than we could.
Then, yesterday, Sahara, our blind Syrian hamster, was eating some peanuts (unsalted and unroasted) on my mouse mat and dropped one off the edge of my desk which I picked up. It made me wonder if rabbits could have an anaphylactic shock to peanuts, in case I'd missed one Sahara had dropped and Ollie had found and eaten it. Hence my being relieved to find peanuts aren't likely to have been the cause.
We still don't know why Ollie died. Very sadly his flatmate, Anna, died five days later, a week shy of her third birthday. She'd been responding to treatment but there's nothing you can do for a broken heart
(Sorry if I haven't go this quite right. It's my first post here.)
Charani