Problem problem!

This is what happens to some deciduous tree species including cannabis in autumn/winter ...in the flowering stage sometimes producing chlorophyll takes up to much energy at the end of its lifecycle ..so its stops producing chlorophyll and the remaining chlorophyll breaks down making the anthocyans ect more prominent ...Engels is nie my eerste taal nie

Your pH is spot on, your nutes are fine... I think it's a bit of a calmag problem myself (give them 1tsp/gallon once a week only) but you should probably also be adding in some extra PK given the stage they're at... Good luck and have a lovely holiday!