15 Attribute point quests for Canthans

So I know there's two quests on Shign Jea Island that give 15 attribute points each...if you do these 2 quests can you still do the 2 quests in Tyria that give 15 points each (thus giving you 30 more attribute points that a tyrian)? If so, is there any way for Tyrian's to make up the 30 point difference?

Sorry if this has already been asked, but search was down.

Nope you can't do the other 15 attribute quests after you've already done the first two in Cantha or vice versa.