You have to keep in mind that each villager eats 3.5 food every 5 mins or so (on 2x). I'm not sure exactly how the numbers work on the hard setting but if it's like the normal that comes out to 42 per person per real hour. I wouldn't leave it on until you have a nice stockpile and farm 3. Really sorry about your villagers, I feel sad when just one dies let alone almost all of them. /hugs