Bug with Punish-Shroom

How can I report a bug in the game? Specifically for the Punish-Shroom. They keep trying to do 2 damage to zombies that are already killed. When you play two together or when they kill more than one of your other mushrooms (with weed spray for example), sometimes they attack the same zombie several times even after it is dead already.

As soon as a zombie's health goes to zero, it should be removed from the field before continuing with the animation of the punish-shrooms.

This was particularly bad when my two shrooms kept attacking a Jester 5 times and I kept getting 2 damage from it on my hero, even though it was down to 0 life after the first attack.

Thanks