Tahm Kench - Devour did no damage

I was playing Tahm Kench with a lvl 3 Devour. I noticed though out the match that my devour was doing no damage to enemies. Lvl 3 devour: Yasuo

1. applied 3 stacks to Yasuo who had around 15% health and a shield up.
2. Devoured and the action was applied with no damage. Upon spit out no damage was applied and his full shield remained

Darius

1. applied 3 stacks to Darius who had around 60% health and a shield up.
2. Devoured Darius and the action was applied with no damage. upon spit out no damage was applied and his shield remained

I've played Tahm alot and have never noticed the issue till today. The devour action was never canceled by the player and full time passed before spit out. It appeared that I was simply removing them from the fight and spitting them back out with their pre-devour health. Has anyone else had this issue?