It should be the hair tips.
The tips of your hair are the oldest section and therefore the most vulnerable to breakage, split ends and fraying. Some fail to retain hair length because this weakness travels up the strand; the dry, weak ends fall off and expose more hair that wasn't vulnerable before leading to the same vulnerability and more breakage.
To stop this from happening give the tips extra moisture. Even when your hair is in braids/twists hydrate the ends at least every other day with a hair cream.
New growth is much less vulnerable to dryness because sebum (the oil naturally produced by the scalp) can travel part of the way up the hair shaft. The kinks, curls and coils of natural black hair make it difficult for this oil to travel all the way to the tips.
- For extra protection, bantu knot your twists so the ends are out of sight.
- When you venture out throw a hat or scarf on for extra end protection, especially in the winter.
Although new growth is less vulnerable, I personally encourage my hair to grow by massaging our essential oil infused hair oil, Neno Natural's Hair Growth Stimulator, into the scalp.
Even if you have braids with extra hair/mesh attached, treat the plaits as though they were your hair by spritzing daily and applying a leave-in conditioner, oil and cream regularly. Your ends will thank you by not breaking off.
Of course, the entire Queen of Kinks product line is designed with moisture retention in mind.