I'm sorry but I don't understand this question.
You say you are adding a sprite when the enemy is attacking, do you mean that you added an attack-animation to your enemy-sprite?
You are creating new enemies every 3 seconds, this I understand.
You also added a sprite for when the enemy is destroyed. Is this a new sprite you spawn, or is this an animation of the enemy sprite?
I don't understand the part of the newly created enemies, I'm sorry.
I think you might mean that the destroyed sprite is happening to all your enemies, but that shouldn't happen if you pick the right sprite. Could you share your events if this is the case?