Hello

Hello I'm not a breeder, just someone with a big heart that thinks mice are adorable. Its 3am and I can't sleep. I went to say goodnight hours ago to my little girl Peanut and found her dead. I've had her two months she was remarkably tame, oddly never used her wheel and her poop was more red- brown than black. I adored her and dismissed the odd traits as her personality.
Last night I noticed what looked like a raisin in her food mix. I thought she might really like that and split it into two pieces. This morning I noticed it missing, she seemed to be unmotivated by food and I smiled to see it gone.
Tonight I noticed what seems to be droplets of blood on the walls of her home and her bedding. I am dumbfounded as to what happened. Was it the raisin? Has she been sick all along. I've kept pet mice before, I dont understand. I am hoping someone here can help me determine what happened. Thank you.