Childrens' Appearance Makes No Sense (Spoilers)

The ghost children appearing throughout the movie are all bandaged. This coincides nicely with the original legend of the niños santos who died in a fire 500 years ago, and the tributes of the bandaged statues that the locals still make every year. However, once we eventually realize that the ghost children are actually those that died 20 years ago from mercury poisoning, their bandaged faces no longer fit. What does that have to do with the mercury poisoning? It's as if the filmmakers shot those scenes (perhaps most of the movie) and then decided to switch gears at the 11th hour, but either ran out of time, money, or desire to reshoot the ghost children. Not that the rest of the film was cohesive or well-made, but this really bothered me. As the viewer you are deceived, with certain assumptions basically shoved down your throat and then abandoned.

Just because your father tried to eat you do we all have to be unhappy .... forever?