She had had pneumonia, and I think she was just too old and tired to want to fight it.
Almost 9 years ago we adopted Amber from a small rescue, who told us that she had been found thrown away in a skip, still inside her hutch. She had to learn to drink water that wasn't in a bottle, and didn't understand about grazing grass until she saw another rabbit do it.
This morning she went out for the last time and sat in the sun for a little while and nibbled the grass. After a little while she fell over, and I took her back inside, where she dozed off and never woke up again.
A good life, and a good death. Goodbye Amber bunny, and sleep well.