I've got 2 (there was 6)eggs under a broody pekin bantam, I've been candling from a couple of days in. at no point have I seen any veins oranything in them.I candled the 4 she had a few days ago at day 12 and two were not fertile, so I threw them away, the other two, one is letting no light through at all, and its the lightest shelled one of the lot, and the other is dark with a large air sack at the base. from what I've read, at day 12 its a bit early for them to be totaly dark like that. is it normal for an egg to have no light through at all and so early? has it just gone really nasty inside?