Minks may be small in size but huge in energy.
The lighting in the first three photos differs from the last three because of a quick change in positioning from north to south by this mink. You never know where a mink is going to pop up (and it's not only weasels that go "pop") and for how long. Sometimes the camera doesn't have the opportunity to re-focus and that doesn't take into account a change in lens length. Mink do have that annoying habit , albeit endearing, of being some distance away, disappearing and then reappearing right in front of you, within spitting distance.
So for all those times that a mink has taken sufficient time to pause the action so that a clear photograph can be taken, I say "thank you"! :)