Lessons Learned - 4x White Widow Auto

My how things quickly can change! As the pots dried out this week there was some obvious discoloration happening on the lower leaves. I've attached some photos to try to determine what it could be. Given my watering never went beyond 7 ph, I'm thinking it's a nutrient issue. I put in a sliver more CalMag and fewer veg nutes this week as these autos will probably flip over to flower mode given the timing and stress.