I think the problem is because you set your event like this:
Touch is touching fam_ducks -> call squishDuck
and inside squishDuck you use this:
System every tick -> duck Tween_squish splash stuff
because the function doesn't pick any duck or fam_ducks, then the action duck Tween_squish applies to ALL DUCKS.
Do you call function squishDuck somewhere else? If not, then maybe you don't need it, and you can just call the tween action at the touching fam_ducks event. I assume this Tween_squish behavior is from the family and not from the individual duck, if so, you can do this:
Touch is touching Fam_Ducks -> Fam_ducks Tween_squish actions
Make sure than you're tweening the Fam_Ducks family and not the duck, because at the event touching Fam_Ducks Construct already picked the member of the family for you to manipulate. If you use duck Tween_squish, it will apply to all the ducks again since your event didn't pick any duck