Penalties for Thursday theatre slot in Trickerion
From the rulebook, page 17:


  When having at least one Character on a Thursday slot, the player subtracts 1 from the Fame and Coin yields of all of his or her Performed Tricks, while when having one on any Sunday slot, he or she adds 1 to the Fame and Coin yields of all of his or her Performed Tricks. This also applies when the player’s Tricks are part of another player’s Performance, and when the player’s Magician is not present in the Theater. If the player has no Characters at all in the Theater when his Tricks are Performed, he receives the same Yield modifiers as the performer.


Seems pretty clear to me: as long as any of your characters are in a Thursday slot, any of your tricks performed that week get the adjusted Fame and Coin, regardless of whether your Magician is present.