Thanks for the fast reply !
I thought about Nitrogen defficy too, but if I give her more Nitrogent, wont I even burn her harder?
It's a "hobby growing soil" which I have been using for my "normal" plants for a long time.
Salt: g/L : <3
Nutrits: 100-500mg/l Nitrogen...
As you can see in my pictures, the leaves of my (4 week old Sour Diesel) have gotten purple. She gets 12/12 for a week now but the leaves have been purple before that.
Some other facts :
temp is ~25 degree Celsius (77F) during lightening and ~23-24 degree Celsius (73,5F-75,2F)...