get thin wool socks, make sure the boot fits and you are cranking the buckles super hard, dry out your liners, blah blah blah. all good ideas but...
the most common thing i found when fiiting the SPKs is that it has a very low instep, right in front of the ankle on top of your foot. Do you notice any pressure marks there? A lot of the time all you have to do is get a good bootfitter to grind a small spot out of the edge of the white shell, just as it overlaps on the black tongue. The bootfitter will line everything up and make sure he is grinding the right spot.
This is obviously an assumption, but could very well be the problem. The boot is biting the top of your foot and cutting of the blood flow to your toes