My best guess is that when the auto-turner was removed, the motor was not there to generate those 2 degrees of heat... I do not think I fiddled with the temperature at all. I charted temp and humidity daily, so I know exactly when it happened and will watch for it this time around. Part of the issue is that the incubator is at my parent's (they have the nice basement with the steady temperatures) and I was only checking once a day. This time i'll run over in the morning before work as well as after to check the eggs. I may get a fan or at least be sure to rotate eggs from inside to outside in case it was a 'hot spot' issue.
Definitely a learning experience, that's for sure!