One of my AGBs died tonight for reasons unknown. Over the past few days, it had turned a grey-brown color and became very, very lethargic and unmoving. I was told that more than likely, this was a sign of an oncoming molt. The molt never came, and the poor millipede has passed on... I was wanting to know what could have caused this greying and sad, slow death. Another one occupies the same tank with it and has not shown any signs of the same problem. It's appetite is still rather robust and it's very active. Any idea what could have killed my AGB? 