You are targeting the Photon.actornr to be destroyed.
So when "on the pc of player A" a sprite is hit.
The actor number of that pc owner is going to get destroyed on the other players pc.
Instead of the sprite you actually want.
Solution is to use the "data" line when you raise a photon event.
Make each sprite have a variable called actornr.
On the "is joined" event of that player sprite set that variable to photon.actornr
Now you have the actornr embedded in the sprite to compare to.
Then on collision with the bullet raise event with event data sprite.actornr
Then on received event.
If sprite.actornr = photon.eventdata(sprite.actornr)
Destroy sprite.
Hope it makes sense