i turned on VV and a window that looked like it was from the tutorial popped up and said, "a little villager is sick! let me help you find a doctor!", but everyone was healthy except for one guy who's at the weakened state, but he's been like that for a while. and then a mushroom popped up in the same spot the one in the tutorial. what does it mean?!

The reason i think for the mushroom, to help you start to get some food from the start.

It means that the tutorial got confused. That happens sometimes if you don't do everything exactly in the order that the tutorial thinks it should be done.

Charley, the reason for the mushroom in the tutorial is so that the player knows that they exist and knows how to pick them. That one mushroom is not enough food to really help very much!