One of my villagers also suddenly died on me. I am on level 2 Medicine. This villager, Kifa, was 66 years old and nursing. There was another male villager, Masau, who was 68 and his health was steadily weakening. Kifa, on the other hand, was elderly and showed 80% on her health bar but still showed very green. After she started nursing, her health bar went to 100% green, and I thot to myself "Hmmm ... so nursing does improve the elderly's health." I took my eye off her for a minute, and then I noticed that she's missing and a pile of skeleton on the ground -- Kifa's remains.

Any idea what happened? Kifa is dead, so is the baby that she was nursing; the population count went down by two. This was a surprise because I had thought that Masou will die first since his health bar is in the red now, while hers was 100% green. I wanted her baby because she's a master farmer and hopefully her genes will pass on to the baby.

P.S. These villagers die very quickly. While I was writing, Masou's healthbar was showing 20% red. I paused in the midst of writing to look at the villagers, and found his skeleton on the ground!