What kind of quail?
First eggs may not have a shell or a thin shell that broke/breaks easy, therefore inticing them to eat them? Once they get a taste, they may continue to eat them even if the shell is normal, in which could be a hard habit to break.
...........or they are just plain malnourished?
Fake eggs (painted stones, etc.) can be placed in nest area (if they have one, some will lay everywhere, depending on environment), this can discourage them from eating the real ones when it becomes futile to try to eat the fake ones.