There’s a cumulative load being applied through the plans but I’m surprised you are suffering from it at the end of the second week, or indeed the first unless you are carrying a lot of fatigue already. You also need to consider life stresses: work, relationships, etc. It’s unusual for someone to nail every single workout, especially if their FTP is in the right ball park, but struggling on lower intensity efforts indicates something isn’t right. You don’t say how old you are or general cycling/training background.
The general recommendation (there’s lots of threads on this) is to look at a lower volume plan and add to it rather than skip workouts in a higher volume plan. A lot of the threads are along the lines of: “I can ride 20hrs a week outdoors is the high volume plan right for me?” Why do low volume then add to it? It’s generally better psychologically to complete a plan and do more than required than feel like you’ve failed to do what’s asked of you.
If you’ve an event X weeks out and your plan leads you to that then either skip the Wednesday easy workout and move Thursday’s workout to Wednesday, etc. so Sunday is free - you could do a Z2 outdoor ride if you felt like it. Or move to the Low Volume plan and simply start at week three.
Alternatively if you are just getting a feel for the whole TR “system” then I’d just move to the Low Volume plan and add whatever Z2 riding you can manage.