IT WAS DEBRIS! I am so so so happy that the duckling is ok! The white duckling seems to be doing amazing and is out of the egg now, no yolk and it was just debris that looked like yolk. Everything looks fine so far and the duckling seems great. I will probably give it sugar water for a few hours like every 30 minutes, I heard that tip on a guide, but if you guys think that isn't the best idea let me know because I don't really have any experience giving sugar water. The other ducklings seem fine although they are still chewing, pastel seems to be chewing less now though and I will probably proceed with opening up the membrane in a little while! I cannot explain how relieved I am about the white duckling.