As the subject says, it seems there is a bug with cooking and slags. I am not sure what caused this to happen but I noticed that my colonists were not eating food they kept trying but would not finish nor would they satisfy their hunger. After forbidding them from the food they were trying to eat they went to the food stock and grabbed a new dish and ate without issue. Upon inspection I noticed there was an extra ingredient in the food: http://i.imgur.com/fpJSSdA.png / Not sure what caused this or how to reproduce.
This is hilarious!
I think your colonists are preparing themselves for Alpha 7 where we will be able to construct stuff out of arbitrary materials.
;D
Talk about some harsh rationing - Maybe they're not getting enough iron in their diets?