Or are they broken due to unhappiness? Broken dwarves don't eat or drink.
They always break first. We don't appear to have enough available to prevent that.
They have spacious private rooms and good food being cooked. Those are some of the only positive modifiers I've been able to generate.
Once the first Dwarf dies things spiral down quickly because good food + spacious private room is about +25 or +30 and seeing a dead body is -50 and carrying a dead body to the graveyard or tomb of the fallen is -55.