Flower Stretch - When should I flip

Flipped these on 12/5

Was away for 9 days and came home to a blown ballast on one of my CMH. Luckily I run 2. Think it must have blown recently as plants look pretty good. Think I really need to check my numbers on next watering. Soil on top seems really hard and crusty. Not sure why.

The 2 AH Autos are so different!

AH-1

AH-2

Purple Kush:

Northern Lights: