Hi, I try to wait 6 weeks then put them into flower but it is up to you, it can be done at 3 weeks or you could wait for 12 weeks. Your plants look great.
First Welcome to ILGM
You could start any time now. Or you can wait a little and let them grow a little bigger it totally up to you and what you want.
But when you do flip to 12/12 they will stretch for the first two weeks or so.
Say after the 4thweek in flower get a magnifier and look at the trichomes.
This is the average time it will take for the flowers(buds) to be ripe, this is the time after the switch to 12/12.
So, as with any strain of cannabis, you need about 8-9 weeks in a 12hr or less photoperiod until finished or ripe. 65 days is just slightly more than 9 weeks.