cheating Pvz hero

I have played several PvP matches and noticed that some players with [edit - CM] usernames seem to be using more than four copies of the same card. I'm not trying to be disrespectful or make assumptions, but this has happened repeatedly.

In the most recent match, the player used the Brain Environment card, then played the Legendary Treasure Chest (which costs only 1 Brain). This allowed them to keep generating and playing the same cards over and over again.

I think this might be a game exploit or cheating. Please investigate this issue and fix it if possible. Thank you.