Possible Yolk sac or worse?

[Copper9Miko1]

I'll post a link here as I posted it under a different thread and thought I should put it here too.

I'm new ish to hathcing chicks and the majority of my chicks hatching being fine not sure what to do or what this is any help would be appreciated thank you.

https://www.backyardchickens.com/threads/unabsorbed-yoke-possibly-help-please.1664998/#post-28615708