Almost 9 weeks old, when can i start the flowering stage?

You could start flower now. They look mature enough and you still get a week or so of solid vegetative growth after you initially switch, not to mention the stretch all plants go thru.

What is the size of your growspace and lighting situation?

Just my 2 cents but I’ve been out of growing for a while so you may want a second opinion

 

put them outside as now we have passed the solstice

be sharp for bugs tho and check daily

good luck