Oh yes, I know about the Florette one Sarah, I didn't read through much but I got the gist and I did see she lost two pigs.
The lady with this guinea believes it was down to a bad bale of hay. She said it wasn't great quality and she withdrew that bale it as soon as she realised it was probably harmful (not just poor quality, but actually harmful), but just those couple of days they were on this hay, one guinea died and this one became very unwell. I think she does have other guineas - may be wrong, but I'm sure she has more - so it could be suspected to be something more specific like a toxic plant or weed in the hay.