Has anyone experienced this? I thought the daily report was based off average vault happiness. I've been getting A-grades since I first started, never lower than that, so this is out of the ordinary. The lowest happiness for a dweller in my vault is 75% (about 15 individuals out of 128), but that would not bring it down to 0% overall. Is not playing daily a factor? Seems like a huge penalty for skipping two days, 0% F-grade. I don't play as much as before, but I returned just to check on training dwellers. Everything is running efficiently, 93% happiness, and nearly full resources.

http://i.imgur.com/52xfFO3.jpg