1) Set your incubator to 89, measured in your egg tub.
2) Put 2-3 inches of Hatchrite in your egg box.
3) Put in eggs.
4) Clear condensation off top of egg box lid once per week.
5) Wait 56 days.
6) Take pictures of your new baby snakes.

It's hard to guess at what happened with your previous clutches but that's my formula and it seems to work well for me...