"Spoiler"; that's what we add when we speak about somethings that other gamers would prefer to discover by themselves.

I'm sorry for your villagers. You must find something else than just mushrooms. Take a villager and bring him around the village looking what is said on the lines at the bottom of the screen.
Or you may try to look at the VV3 guides, there are some tips that could help you!!

You may also look ar this thread in Forums » Windows/Mac Games (and Palm/Pocket PC) » Virtual Villagers 3: The Secret City » My villagers are dying!! What am I doing wrong?