Nobles just "drop dead" with no explanation

Yesterday I had three nobles just randomly drop dead. One was my leader. I only knew she was dead because I got the monologue from the "gods" about it.

The first time I went back to a previous save and made sure the leader had plenty of sleep, food, clothes, comfort, etc. She did. But she still just randomly dropped dead the second time anyway. I was not under attack, and the entire kingdom was at full health at that time. Also the second time, two others randomly died at the same time she did.

I'm not sure if this was from "old age" since I had been playing with her as my leader for a LONG while, but it's possible. I don't have any explanation in the activity log. So if we could get something there explaining why nobles suddenly drop dead (age, lack of food, lack of sleep, etc.) it would be much more helpful than just a random death that may actually be a bug.