Out of curiosity, what were the temps in his bathroom sink cabinets during those times? Were the babies healthy and normal size etc.? Can you ask him? I have already bought the materials and decided to build a bigger incubator this year, but I will probably outgrow it again in a couple years. Space is the main issue here.
It seems that eggs don't die within range even if the temps are not exactly constant, just takes longer to hatch?