A slow poison was injected into the food supplies of your animals and slaves.  Fortunately you discovered it before any permanent damage was done.  But the victims are quite weak.

A natural deposit of uranium has caused a mild case of radiation sickness to break out amongst your living inventories.

The mosquitos this month have been so bad that all your slaves and livestock are suffering from blood loss.

Drafty living quarters and rotten blankets have caused health problems in your living inventory.

A rival king has constructed a still on your lands.  Your slaves and animals are all hung-over.

The water from the wells has been brackish lately.  Your slaves and animals have been out of sorts.

Something must have been wrong with the slave's and animal's food.  They seem to be suffering from severe diarrhea.

Your slaves and animals seem unusually slow and iritable lately.

The hot dry weather has made everyone listless and weak.

The weather has been cool and damp, and everyone seems to have colds.