Thanks for the feedback. While I had wanted to have red targets increase health, I was concerned about it becoming possible to reach absurdly high amounts of health because of it which would make it very difficult to lose.
As it is now the red targets reaching the turret only increases score, but I may add in the targets increasing health in the future if I can figure something out. Additionally, the health increases at a slower rate than enemy health to help ensure the game doesn't drag on too long.