I know I have had people say not to pull them until day 15. Myself I have had them blank until day 12. After that they just look iffy. I pulled a few eggs once and thought they were junk, then broke them into the garbage can. Was sick when I saw the baby chick/blood/fetal mass whatever you want to call it. Now I hardly ever throw, unless I am positive it is a clear.
Aww, that's unfortunate I haven't done that yet but I think it's because I'm over paranoid about doing it. I have 13 BCM eggs in the bator now and I don't dare crack them open. I'll toss what doesn't hatch. I can't even begin to guess if they are developing our not lol. There are a couple that I think might be clear but I don't dare risk it.
Cream Crested Legbars, BCM, Rhodebars, bearded silkies, good laced/buff laced polish, black/lavender ameraucanas
Bourbon red, red bronze, royal palm, mottled black
I also make hen saddles, PM me for details!