Phosphorous lockup happens, and I've seen it, usually I see that from the cold nights later in the season. This, however, as much as everyone disagrees, is a fungus or disease of some sort. Cannabis literally has hundreds of diseases that attack it, including one that can spread from plant to human. This purple-grey mess mutates and wrinkles plants from top to bottom, curls and twists the leaves, makes the plant vulnerable to bud rot, and reduces the bud to tiny little mutated popcorn buds. Neem oil helps to an extent, something that absolutely would not help with phosphorous lockup. Plants that are more crowded by the native weeds get it a lot worse indicating that to an extent air flow helps, but the spores are in the area and every year it effects at least one or two to varying degrees. Some plants seems completely unaffected by it. Also, while I've been growing in that spot for 11years now, several years I've grown in another location (one at a higher location more at risk of cold snaps) and not had the problem in that area.