Oh yes, the guns haven´t been changed since the craft were built (23mm turrets have been upgraded as you said), but one of the four twin SSM-launcher was removed to make room for the Sonac PTA. So lately the total armament has been a bit different than earlier, better?Well weren't you saying they´ve lately been equipped with the guns you mentioned??
But the Helsinki class had always featured the 57mm and the 23mm from the start. (which the latters however was changed to new turret models which could launch the Mistral SAM as well)
Between Helsinki and Hamina class there was a Rauma class which was slightly smaller boat and thus featured smaller 40mm gun. As the current Hamina class was derivated from the later it orginally had 40mm gun solely, but was later one substituted with the new generation 57mm gun.
I think Mistrals have never been installed aboard these craft, am I right? It is possible, though.