After 5 weeks in vegetativ state I switched to flowering state. The plant indicates that she is ready by showing the first female pre-flowers.
I added 30g of Green House Feeding BioBloom as top dressing.
The lights are switched on during the night (9:15pm-9:15am) to keep the canopy temperature as cool as possible.
I also increased my SanLight from 50% to 66% to keep up with the DLI to limit the expected stretch of the plant (that's my theory).