.

I would think you can still max them so long as you wait to do atleast one of that specific mastery level's quests that yield sp until after you've maxed all of the mastery's skills. Of course this is just a random guess that the problem is that you have 1 more sp than you should, and the game might not count the sp from quests that you've yet to do towards the total sp for that mastery.

I believe that Hiepocrite is asking which skills he/she should add skill points into first, and not whether all the skills in the Sixth Mastery Tier/Growth can be levelled up to their maximum skill levels.

Oh, and yes, all skills in the Sixth Mastery Tier/Growth can be levelled up to their maximum skill levels.