I candled the eggs before I placed them in incubator and for the heck of it I decided to recandle today, day 4. All of the eggs developed this dark spot on the yolk but there’s no visible veins or an air sac. I’m going to candle again on day 7. but does this look promising or will only time tell? Super anxious due to this being my first incubation batch.
(Second photo is edited)
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I've noticed changes like this which do indicate a fertile eggs. Still too early to call but it's a good chance they are fertile.
Is the egg from your first and second group of pictures the same egg? It look less developed but that could also be the angle.