Catching a fade?

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.