if it is showing one linked account then only one is linked... log into account management for each account and one of them will show that they are also linked to your main. i will warn you if only two of five are getting 300% XP then you will end up with an issue like mine, 2 accounts at 12 and three at 5

Also "linking" only comes into play for RAF accounts created after the program began, if they were created before RAF, they will NOT show anything on the RAF screen.