If your hatches have been late then it is for sure the temps in the bator are off. What incubator are you using?
You need to try to read temps at the egg level. If you are using a basic LG still air your air temps should be 101 - 102 at the top of the eggs.
The water wiggler should read 99.5. I have found the temps in a water wiggler are best used in a circulated air incubator.
You won't get good accurate temp readings if you don't put the entire thermometer in the incubator. The probe is most likely giving you an ambient air temp at its highest reading.