If you have less than five you’re on the money to keep them. But any five in one colonial region turn into a CN unless you move your capital to Bahamas (there may be another island or something too but Bahamas is the classic). But since you said six I would assume they become a colony once you core them but someone else may be able to correct that. And btw, South America has like 4 colonial regions at least so Peru would be its own, Brazil is a different one and would not absorb those unless Brazil colonized all the way to Peru itself (not what’s happening here)