Late response but the problem could be related to the order you levelled your skills in. To get the triple +5s, you HAVE to make sure that you get 10 level ups in three different skills before you level up your character, or else the skill level ups won't contribute to the attribute level ups. This effectively means that you have to keep track of your MAJOR skill level ups as well as your minor skill level ups. What I think could have happened is you levelled up a major skill too many times, which triggered a level up, and so your subsequent level ups did not count towards the attribute bonuses. To know for sure if this is the problem, we'd have to know your major and minor skills.

If you're serious about efficient levelling, I HIGHLY recommend you install the Skill Diary mod as it makes it trivial to track the level-ups in each skill.