The holes are there for air exchange but it was also vented when we opened to turn the eggs. That is why we didn't put a lot of holes.
I think I will chech the humidity at least to confirm that we are in the right ball park, to see if that one sponge is the right size or it needs more.
How do you know when the hygrometer is not measuring right? I would 't know the difference.
Opening and turning the eggs, adding warm water will not effect anything for the first 18 days(chickens) the last 3 or 4 is debatable----being a Hands Off hatcher I do not open my incubator from lock down to all eggs hatch---or day 22 For Nothing!! Adding water by other means(through a vent hole, etc) To become a hands on hatcher there is a lot of things you need to learn before attempting that to have a Great Hatch.(How was that Amy)
There is ways to check the hygrometer--you can google/search for that info.