Assign the turret family a hit variable, call it turhits. when your turret gets hit, up turhits by 1. create a text object called showhits. It is a small square that holds a number from 0 to 3.
Every tic delete all showhits. For each turret then create a showhits text object and put it on top of the turret (or close where you want the number of hits to show). write that turrets turhits variable into the showhits text object.
This looks like it is a waste of computer time but it will work fine and you will never see it slow you down by even a single frame.
yours
winkr7