Hey
@L0opinG , you have pretty standard potassium deficiency, it looks purple or blue due to genetics, but basically the plant needs P+K (K is potassium) during flower. If you add any standard PK nutrient the leaves wont recover but the problem will stop spreading. Simply put : you do need a PK booster because the soil doesnt have enough of it because the plant is in overdrive due to the 20h light schedule and the plant's high metabolism due to temp and humidity ration (VPD)... this will affect your yield if you dont fix it but it wont affect the taste... hope this helps bro ! 🚀