I am laughing because that is the first thing my shop told me to do.Are you referring to Mares X-Stream fins?
Any chance you just have them over tightened or have the wrong size?
If that is US size 9, that isn’t right on the border between size S and R.
And any chance you haven’t removed the plastic packing insert from the foot pocket?
(Don’t laugh, it’s happened before...)
But yes, its the Mares X-treme