No idea as to what caused the diarrhoea, death was likely due to systemic failure. They had concerns about his kidneys with all the meds he was getting.
Thanks everyone for the hugs, they are much appreciated.
Yes BB he was that foal. Makes me so discouraged with horses sometimes. I am just angry and want him back. Seems I was more attached to him than I realized. He was such a fantastic foal. Everyone loved him. Darien is having a particularly hard time of it.