I just built 10 or so new wheat farms, since 17 can't produce enough wheat to keep 24 people fed all the time.
EDIT: are ghosts of fallen heroes spawned by human remains, too? I thought they only came out of graves but I've had 2 jump my citizens as they were out getting wood (one of the killed a citizen then was killed by a second citizen, but the second ghost was noticed by other citizens passing by and 5 people ganged up on him) and I have a bunch of remains in random places in the wild due to all sorts of problems. Brownie hunters, yetis, giant spider sieges...