Surprise death of fosh

[dromo2189]

Hello I have a pearl scale butterfly for over two week now. He was doing great until I just came home and found him dead. Last night and even this morning he was fine. I don't get what happened. When I pulled him out he has this slim on him which I thought was weird. Any ideas? I have a picture of it will help

 

[dromo2189]

Here is the picture