You’re setting the same timer repeatedly.
In fact, not even one timer is running properly, because the execute pin of the for loop, will run this in one frame
But before the timer gets used, the next frame will happen.
If you want a timer for each object, you can make an array of timer handles. What is much easier, is to do this in the blueprint of the hit objects 
Yeah, I just had a quick go, don’t do it 
Arrays of actors and timer handles, and it’s not a good method.
Just have that damage on timer stuff in the actor, and call it for each actor in the for loop.
Maybe this
but still not great 