Actually, Nuzlocke challenge isn't official, it has come from a comic series. There are only two basic Nuzlocke rules:
> Any Pokémon that faints is considered dead, and must be released or put in the Pokémon Storage System permanently.
The player may only catch the first Pokémon encountered in each area, and none else. If the first Pokémon encountered faints or flees, there are no second chances. If the first encounter in the area is a Double Battle in dark grass, the player may choose which of the two Pokémon they would like to catch. If there's a static encounter in the area, the player is allowed to capture them despite already capturing a Pokémon in that area. Shiny Pokémon also do not apply to this rule.
Source
Any other rules are fanmade.
You are allowed to make your own rule as a mercy or hard rules on Nuzlocke, so it's just your own choice. There are no specific rules about poke pelago.
