This happened to me, but my two does we’re in separate runs from each other Each with a neutered buck with them. I fed them all in the morning and they were fine went out and my doe was having a fit and died, the next morning the exact same thing happened with my other doe but before I fed them and both bucks were fine, then two days later my next door neighbours doe had a fit and died. I have been searching to see what it could be as I can’t afford to get a post-mortem, but now reading this and knowing my neighbour has 4 cats that I do see quite a lot in my garden I think this could be the cause, but not sure why it would just harm the does and not the bucks.