Goodness, Onthespot...what a problem. Sounds like the goose eggs might have been incubated differing amounts of time. If one is very dark with huge air sac sounds like it is/was about there.
With goose eggs at about four days, with a good egg lume, one can just see like a sort of circle mark in the yolk with a darker rim & perhaps a little dot.
Good luck
With goose eggs at about four days, with a good egg lume, one can just see like a sort of circle mark in the yolk with a darker rim & perhaps a little dot.
Good luck