You did nothing wrong, you did all you could. If there had been anything missing in your care, the vet would have told you and you would have been able to rectify it but the very very sad fact is that abandoned kittens are usually abandoned because their mum knows they are not going to make it. It is very, very hard to raise an orphaned kitten, the hard fact is that up to 40% of them die, and all of us who have tried to help orphaned kittens have had them die on us. It is devastating but you can’t blame yourself. It is sometimes called ‘fading kitten’ syndrome, a kitten that seems fine suddenly starts to fade, but we don’t know why. There are so many things that could have gone wrong during the mum’s pregnancy and birth — not enough nutrition, birth trauma, viruses, mum’s blood being incompatible with baby’s, baby not having its mother’s antibodies any more so its immune system becomes very vulnerable — and we will never know why.
But if you hadn’t found this baby, and given him love and care and food and medical attention, think how lonely and sad his death would have been. He was cherished all of his short life since he found you and though it was such a brief and tragic life, it was a happy one. Think of what you gave him. {{{HUGS}}}