Best wishes with that, hopefully it's just an isolated case. Even if they all turn out bad, these things happen sometimes, illness can sneak through a flock while they all look fine and all you may see is weak eggs -- IF you candle them before you sell them, that is! If all the eggs are bad, maybe you should suggest to her she may want to candle her eggs before she ships them... She may have stopped checking because most were healthy and a bad batch has snuck past her. Weak shelled eggs can hatch successfully but under normal circumstances they're just a waste of resources because most fail.
I candled the rest of my eggs a couple of hours ago, and that one is the only one that has those lines. There are 4 where I can see the embryo/veins for sure, 2 that I can see dark masses (but can't make out any veins), 2 that are clear (including the one from the first post), and 5 marans eggs that I can't see into.
Do you have some system of identification set up? It will be very educational for you to be able to identify each egg separately and chart its progress with photographs and notes, for future reference. Beats trying to recall a vague and isolated incident years back where an egg looked 'just like this one' but hatched successfully, or didn't, but what was that other little tidbit of info linked to this case... Possible cause, or possible correlation, or side note I needed to investigate...? LOL. It gets even messier when the adults that come from a certain development 'style' turn out a certain way or produce offspring that turn out a certain way and you need to draw all the information together. Beginning a livestock journal is a literal lifesaver for your animals and will be of great assistance to you. It sometimes seems like another bit of work but it will be invaluable at other times, so if you don't have one I'd really recommend you do yourself a favor and start one. It doesn't have to be just like the industry standard, just record what you want to know precisely in future. In fact there's software for this too, lol.
Ok, off-topic aside, how old are the eggs? All 80 hours or so? Some eggs develop slower than others so the clear ones may still be fertile but if they show no significant change before the end of the week, I'd chuck them. As for the too-dark eggs, a more powerful torch will help.
This is the best picture that I got, from one of the Ameraucana eggs. It's normal for the yolk/embryo to float to the top of the egg, correct?
What's normal isn't cookie-cutter precise, there can be deficiencies or genetic influences that cause abnormal development which can still result in a live chick but which can cause issues like failure to pip, requiring assistance hatching, propagation of the trait for malpositioned chicks etc. Some times you get chicks which hatch prematurely.
Some movement is normal but if it actually floats right to the top of the egg I'd be suspicious of it, especially if it moves very fast. There are different layers in the egg supposed to hold the yolk etc where it belongs, and if it's moving through those layers perhaps its internal integrity is badly compromised.
Now I am a little worried about air sacs, though. I let them sit for a few hours upright to warm up, then left them in the incubator upright for 2 days, before I began manually turning in the carton on the third day.
I've only used hens for incubation so I'm no help there, but why did you leave them sitting upright for a few days? I take it this was based on some advice you received somewhere... But it seems odd to me. In the natural circumstance eggs do not sit upright for prolonged periods. I could see how it could be useful after shipping in resetting the air cells back into the proper place if they were dislodged, I guess. Theoretically it wouldn't do any harm, either way.
Anyway, best wishes with them. One thing they can do is appear to be developing along normal guidelines when actually they died early on. That's a confusing one.
