Auto Brothers: Mimosa and Northern Light

It's an auto, flowering wekk 4 isn't unusual. You main issue is that she doesn't grow that much in 4 weeks... Small container not breathing, poor soil, oe weather.... Actually, September day might be fine... But if the nights goes under 15°C, it's maybe slowing-down your plant. I started an auto outdoor like you, 3 weeks ago. She grew 2 nodes, when indoors plants (not autos) got 6 nodes... You must know that a small container will tend to trigger flowering faster.