15L pot is huge for such low wattage lights, the pots in my pics are 2L.
With regards to watering you have to train yourself to know when the pot is light, get to know the weight (even use a scale at first) when it's just watered and the weight when the topsoil is dry. It takes a while but you get the feel in the end.
The weight of a pot that needs watering is at least a quarter of a freshly-waterd pot (rough guide, probably less than a q).
Lockout isn't to do with the amount of runoff, but the high pH stopping the plant absorbing the nutrients.
Here is a good graphic for pH versus the perfect points for nutrient absorption :
You say you didn't use nutes until the sickness started ?
My regime for soil was nothing for the first two weeks (in a light soil mix like yours is and mine was), and then i would start on 1ml per Litre of veg nutes.
A great guideline about the general lifecycle is here :
https://www.autoflower.org/f44/life-cycle-auto-flowering-cannabis-5113.html
And don't stop asking questions!
Two questions aren't enough
I'm awake for another half hour so bang away bro
All the best,
steely
With regards to watering you have to train yourself to know when the pot is light, get to know the weight (even use a scale at first) when it's just watered and the weight when the topsoil is dry. It takes a while but you get the feel in the end.
The weight of a pot that needs watering is at least a quarter of a freshly-waterd pot (rough guide, probably less than a q).
Lockout isn't to do with the amount of runoff, but the high pH stopping the plant absorbing the nutrients.
Here is a good graphic for pH versus the perfect points for nutrient absorption :

You say you didn't use nutes until the sickness started ?
My regime for soil was nothing for the first two weeks (in a light soil mix like yours is and mine was), and then i would start on 1ml per Litre of veg nutes.
A great guideline about the general lifecycle is here :
https://www.autoflower.org/f44/life-cycle-auto-flowering-cannabis-5113.html
And don't stop asking questions!
Two questions aren't enough
I'm awake for another half hour so bang away bro
All the best,
steely