According to your diary you are using a veg nute still. A Bloom nutrient would be better now your in this phase of the grow because the plant is starting to need less nitrogen and more potassium and phosphorus.
Looks genetic to me which means its completely fine and normal my biscottis are doing this just means they are going to finish being purple bud it could also mean your water temps are too low when watering :) best of luck buddy.