If you think its your humidity you may need a wet bulb thermometer or other device to check it and maintain it according to the hatch time.
Some people use the dry method and they say it works for them other words they do not add water to the Incubator.
Its a combination of a lot of conditions but the highest on my list would be Temp change the more steady you can keep your temp around 99 to 100 degrees.
next would be turning the eggs minimum of 3 to 4 times a day 7 times works for me.
it would be a pain to have to turn by hand for 25 days with the turkey eggs.
After doing it by hand for my Chicken eggs the first time that's why I made my own egg turner half the price of the store bought ones.
I also am a fan of a fan forced air is better for air circulation and temp control I used a computer fan from a old computer.
I use 2 50 watt light bulbs for the heat Yellow in color I use two in case one burns out and the temp will not fall and when I catch it I can replace the burnt out bulb.
I used a bread crumb can mounting a light inside to use as a candler for checking my eggs.
After 2 weeks I check my eggs and if I dont see any change at all I will dispose of the ones that are bad or not fertile.
Best of luck to you.