What's wrong?

As you can see it's started with older leaves and continues to new. I've search about potassium Def but I'm not experienced grower so it's up to you guys.

I don't feed her yet she is 3 weeks old

I'm not experienced grower as well, but it could be pH problems + watering issues.
Not enough data do diagnose correctly.

Dude, temps, humid., lights, space, food, etc? Give us some info..

Yea sorry.
Autoflower 3 weeks old
Biobizz light mix soil
125w CFL dual spectrum
Temps average 26c
Humidity 50
Ph runoff after watering 6.5 (no nutes yes)
I watering with tap water (leave it 2-3 days open in room)
Wet weight 1377g
Dry weight 846g

Are you overwatering?

I don't know.. I water around 6 days. Leaves never dropped after watering