Looking for advice day 35 auto first grow

Hey people this is my dark devil auto its 5 week today and its been in flower for 3 week almost....I am planning on using pk13/14 on it next Sunday can I starting feeding it in low amounts now then on Sunday go full or just wait till next sunday and then start using it?? Any advice welcome

I would feed it lightly. My understanding is autos don't need as much food as regular plants do.