Tower shot does no damage (video attached)

This just happened in one of my ranked games. If you watch the replay, Blitz takes 2 tower shots. The first functions like normal but for some reason the second shot doesn't do any damage? I clicked on Blitz in the replay so you can see that his health bar does not deplete at all the moment the second shot hits him.

EDIT: I realize the health bar above Blitzcrank's head is covered up by the scoreboard, however, you can still see his health bar in the bottom left corner of the screen. You might have to go into full screen to read it better.