When to start flush ?

Ive had a hard time with this plant and she's so far behind. This is my very first plant and ive had a lot of bumps. So any idea about when I should start the flush ?

That plant still has 4-6 weeks left by the looks of it

My brother had an autoflower that didnt start flowering for like 6 months lol. Off topic I know sorry.

Yea i knew she had a little bit to go

There is no need to flush,feed to the end.