The temp didn't change, the air is stratified in the incubator and the change in where you had your thermometer reflected that. You need multiple thermometers, and the eggs turning helps them to not be dramatically different temps top to bottom internally- since they're fluid it's not really an issue.
The still air can work well if you give it a chance and don't change the thermostat more frequently than once in 24 hours.
I don't even LOOK at humidity until day 18. I use 2 different incubators: one for 1-18, one for 19-21. I have the one with the turner dry as the air is naturally, no water, 99-100 degrees at the middle of the egg as dictated by several aquarium thermometers which sit down in the middle between eggs.
I use another for the hatcher, with paper towels rolled up and stuffed down in the channels for water, with as much water as they will hold, then another paper towel on top of the wire, under the eggs, which is soaking wet as the water wicks up into it. The humidity is very high, and I ignore it unless it drops below 65%.
I open the incubator once or twice a day using the little window- I always use an LG for the hatcher so I can do this- it keeps them from having a dramatic change in temp and humidity. I candle and rotate them if they've pipped on the bottom, etc.
I can't stress HOW IMPORTANT having multiple thermometers is, nor how important it is to toss the cardboard thermometers you get with the incubators. The cardboard expands and shrinks with humidity and changes how accurate it is- this is a huge problem when a little line can mean it's way too hot or cold.
Also, I do move my eggs around every few days in the turner, as there are spots more hot or cold in there. I have used forced air, but didn't think it made that big of a difference. I recommend the RCom-20 if one can save up the money to get one- it's a push-button, turn-key solution that needs no care at all.
