Hi again beejay !
Just been looking at Sky Rules for Capt changes, not sure if this makes it any clearer. I have a similar issue with Suarez as he has been my Capt from day 1 but not scoring double. He had a yellow card so doubles to -2 because of that.
CAPTAIN CHANGES: Managers may make one captain change each game week throughout the Game. The game week runs from Saturday to Friday and to be effective for a game week, captain changes must be completed before the first Premier League kick-off in a game week to be eligible for that game week. Captain changes made after the kick-off of the first scheduled game in a game week will be effective from the first scheduled Premier League kick-off of the next game week. The nominated captain will score double points both positive and negative. Sky Sports and GFM will not be responsible for incomplete captain changes, captain changes lost in transmission or captain changes received late due to high online and app traffic levels. Captain changes may only be made on the Game Website at
http://fantasyfootball.skysports.com or via the mobile game app.