At what point should you write an addendum to address a substantial increase in LSAT score from Sept 2016 to Dec 2016 score? 6 points? 10 points? And if there is no good reason (medical emergency, family death, etc.), besides focusing on better self care, is it even worth addressing?

Additionally, although schools may not report your lower LSAT score for data/ranking purposes, it is still included in your application for all eyes to see (and judge). How much can this affect your application's competitiveness?