Also my temp has been 99.5 to 100.0 this whole time and have not had any spikes or lows. My humidity has stayed around 40-45% with little to no water added. I have hatched tons of successful hatches doing everything the exact same way with no rotten eggs.
I had the exact same thing happen to me today! And I am a heavy candler, I candle at least 3-4 times before lockdown and I check each egg before I set them for cracks, detached aircells on shipped eggs, etc. I had bought shipped eggs and we are on day 6. I hand turn my eggs and this afternoon...