Plot hole: Rex is in the hospital for having a minor heart attack and is awaiting surgery to receive a pacemaker. 1) He isn't connected to an ECG or any other heart monitor so no one is aware of his heart attack. 2) They ran blood tests and checked his potassium levels. They would have also checked the concentration of his medication in his blood. (This should have been done earlier in the season too when they first discovered his medications were not working.) Zero concentration of medication in his blood could throw suspicions on his wife just as easily intentionally giving him potassium.
Factual error: This is for one episode 1-23. In the beginning, there is a shot of a calendar for March 1990. It shows March 1st being a Wednesday. March 1, 1990 was a Thursday.
Chosen answer: Poker. They have been playing that this whole time, once a week with everyone who was invited that lived on the Lane.