I would say it more likely that the extra fan messed with your temperature and possibly your humidity levels. But there are so many variables that can contribute to a lousy hatch. Can I ask why you thought you needed an extra fan when your previous hatch had been so successful? 14 out of 17 is pretty darn good! Extra fresh air is not a bad thing which is why I, and some other folks on here, recommend ditching the vent plugs on the bator lids.
I was thinking I had hot spots because I was getting drunk frenzy temp readings in different spots with different thermometers. But after I installed the fan and had the next batch going found out the thermometers were out of calibration.
Yup, essential to have instruments that you are absolutely sure about, at least to be able to note that one runs high the other a little low, etc. so you can make safe decisions. My incubator thermometer runs a full degree too low and I have 2 other calibrated thermometers in the bator that are within a 10th degree of each other so I rely on them, always.
