I am so sorry. You did nothing wrong. Twins are rare to hatch because there isn't enough room for both if them inside the shell, it's made for one bird only. Usually one dies right before lock down which will generally kill the other developing bird too. Twins hatch but it's very rare. I am super sorry.I have no idea what happened had almost full absorbed it's yolk. There was only one but it passed and stopped moving. I looked through the egg and all I could find was the second yolk was very nasty and the baby had it in its nose and mouth