I understand how you feel. I had an alpaca that I had for 3 weeks, and he was under weight when I got him as a rescued alpaca. He continued to decline, and I made sure he hate as much as the large female llama we had as well, but because he was really wild, I did not know how emaciated he had become because of all of his very long hair. He ate as much as he wanted, but one morning he was laying on his side, paralyzed, and with all the signs I realized he had come to me with the menengial worm, which they can contract. A vet came out and put him to sleep, and I know she felt he had just been starved to death, and she said she have not dealt with Alpacas before and knew nothing of illnesses they get, but I felt so bad that I know she felt I'd just not fed him.
So anyhow, I know how that feels. . .