Personally, I do not lower the temperature at lockdown. I stop turning the eggs and raise the humidity when I start lockdown.
If you do lower the temperature, it is not critical that it happens at the exact same time time as you raise the humidity. It does not even matter that you go into...
Read Hatching Eggs 101 by @Sally Sunshine
Use the same procedure as for chicken eggs except that turkeys take 28 days to hatch.
The incubator temperature will depend on whether you are using a still air or a forced air incubator.
I try to incubate at 30% humidity and switch to 65% to 70%...