Bro, I saw your diary and you use Biobizz, me too haha! xD
Your girls are beautiful. Nothing to worry about too much. Great job!!!
I think it's because you're using 3ml/L of Bio-grow in the fourth week of flowering; normally, nitrogen consumption decreases as flowering progresses.
If you measure the ppm of the runoff water, we will probably find high values, and the babies don't like soil with too much mineral load. Sometimes when that happens, a blockage occurs, leading to a deficiency of some nutrient.
I recommend starting to lower the dose of Bio-grow; that will improve the soil's ppm. Measure the ppm of runoff and irrigation water.
I saw burnt leaf tips and partially curled leaf tips.
Good smokes! πͺ