New Cut Flowering Under Veg Lighting?

[stateraised]

I cut three clones from the same mother that was grown from seed. Week 4 going into week 5, only one of the clones is starting to flower under veg. lighting schedule. Any ideas on what has cause just one of three to start flower under veg lighting?

 

[stonestacker]

The plant was too immature to go into flower?