First time blackberry gum auto outdoor

This week they continued growing at about the same pace as the week before. They are almost 40cm now (15inch) and all three are growing at a similar pace. I started using 5ml of organic boom boom spray in order to give them a nutrient boost during this flowering period. One plant as can be seen on one of the pictures is starting to growing a sturdy side branch. The other two plants are a little behind with side branches. One plant as seen on the cover foto has purple/blue buds. Will the others also turn this color? It looks pretty cool.