deficiency

don't flush for a week in bloom. But, that likely started before 8 days ago, unfortunately. pH in line? if not, fix that first, then think about adding or removing something. interveinal, so maybe Mg -deficiency? give 1g/gallon of epsom salt (aka MgSO4 aka mag-sulfate) i'd resume a feeding schedule ASAP otherwise. But i think you need something extra beyond what you were giving it before. somethign is missing or out of balance or pH is off.

El color rojo-púrpura en las hojas más viejas indica deficiencia de fósforo.

Your plants’ symptoms are pointing to nutrient deficiencies, however it might not need more nutrients, the nutrients may have just become unavailability due to pH lockouts, nutrient salt toxicity lockouts, and or over watering, or any combination of them. Excessive fungus gnats is often a symptom of over watering. Red/purple stems can be a nutrient deficiency of phosphorous and/or sometimes a cal-mag deficiency. Happy growing,

To me it looks like a potassium deficiency but hard to tell with the blue spectrum. But I see all the signs