LizGio
Songster
I suggest a meat thermometer to occasionally check accuracy. The have to be somewhat accurate according to FDA (I believe) also govee has been pretty reliableOh good then it sounds like it is probably not disease-related and it is incubation related.
Make sure you get at least one thermometer to calibrate. Get another humidity gauge to salt test before you set eggs again.
Having stable study, temperature and humidity can prevent stuff like this. Having your incubator indoors in a controlled environment is highly recommended if you have an outside currently.