My hova and lg don't start to fog until 70-75% which is borderline. The windows don't completely fog until 80% which results in definite losses in my bators. It does depend on your bator and even your climate but if the windows are completely fogged it should be at least in the 70s. It would...
If you haven't I would pull the vent plugs. Do you have a humidity gauge in there? The humidity will spike when they start hatching but that doesn't mean it can't spike too much and drown the ones that aren't as far along. I ended up adding holes to my hova to vent more humidity when I had...