I am so sorry to hear this. How disappointing! I don't know if you do 'eggtopsies' (I don't), but perhaps this info can help figure out what happened: https://extension.illinois.edu/eggs/res24-00.html
Is there any chance there was a temporary power outtage that you were unaware of?
Yes I do eggtopsies lol I’m not squeamish so I tend to look at everything.
I candle first then crack. On candle the eggs AC were fine(large and dipped for hatching) no veins, but lots of liquid. When I cracked them open chicks were all sizes. Some the proper size and some very small. The small ones were alive at last candle before lockdown. Yolk was absorbed on the bigger ones but the small ones still had a half pea size yolk.