Pets dying ?????

I've long had problems with certain pets not eating despite having full food dishes that are not blocked in any way, but I've never seen a pet die from starvation. I had one get taken away because he refused to eat and would only whine for walks all day. I mention this because it could be a cause for the frequent orange portraits, and also isn't there a bug with the wellness treat that gives them a permanent "scared by the vet" moodlet? That could be another cause. 

As for the actual dying, that sounds likely mod related because I don't believe pets can die in that manner in the vanilla game. Unless somehow your social worker/adoption agent is broken?