Champions play until they get it right

overfed ? some start to grow, some show magnesium issues, some heavy dark and stagnant aka nitrogen toxicity almost. slow down a bit with feeding. ph is very very very very important. i have aquarium ph drops test kit, always was putting against ph meter every few weeks or more often, just to know is my meter lieing and needs calibration.

You're past the point to do an affective scrog mate. Lollipop with the shoots that are far behind and this will push energy past these points that would of sucked it up "the energy" so basically jst clean up the end.

Deficiency of calcium and generally under fed too. Each and every plant will need s slightly custom feeding schedule, especially when gowing multiple stains.....what might be ok for a hybrid may be too much for a Sativa and not enough for an Indica. Giving multiple strains one generic blend of ferts is not going to work across the board generally. Septoria is so rare, it is virtually never the cause of issues. Up your dosage of cal/mag for a start and think more generally about what each plant is telling you and you might have to experiment with 4 different fertilizer schedules......one for each plant.

A fade is a controlled deficiency.. an intentionally caused deficiency. It is relatively inconsequential as long as it has "enough" to make it to harvest date. Starving a plant that is otherwise healthy has no impact on mineral contentn of flower mass -- this is fact, not opinion. we have the equipemnt to measure such things accurately and have done so repeatedly. i would suggest only causing such a thing when there is a visible toxicity occuring, which is the typical cause for a flush or reducing fertilizer given. purple late in flower could be genetics.. could be sub-68F temps at night.. could be a combination of both. If not temperature related, can be unavoidable. Some plants simply will do it at end of life - exotic colors.