there is no right or wrong, in sending the plants into flower. thats the big fun in Photoperiosd,
you can do it every time. It depends in you.. your growstyle, trimmimg style and growspace.
in long term think about getting a stronger light, plants are growing very tall with big internodes,, that says me you light is not to strong
and weed loves biiiig light.
But back to the plants.... as they are quite tall, yes, i would send them into flower. girls look fine,,, stay with your vegetation feeding, because girls will need nitrogen for the growth iin the beginning of flower. If they stopped stretching, change to flowering nutes
Happy growing