Oh Susanne, I am so sorry for your (and Mingus's too) loss. I think all of us can sympathize and most can empathize with your heartbreak. As as much as we feel about the situation...my heart really goes out to his buddies. I remember your kind, wonderful words when I lost one of my horses, and I hope to return the same to you. Take the time to sit and remember him, hug a horsey neck, and cry into their mane.
On a more medical note...without a full post mortem examination, I would not go as far as to lay the cause of his colic at the foot of his previous life. This long after them, and none of them being major colic surgery/handling bowel/resections, etc, makes me wary of presumptively diagnosing those procedures as the cause. Horses, are, unfortunately, so very prone to colic, no matter what.