Turning yellowish - the leaves


#1

A question from a fellow grower:

The 10 seeds arrived, and I planted 6 of them. So far 5 have sprouted!

My problem or concern is that those that have sprouted and are about 2/3 inched tall, roots beginning to grow out of the bottom (hydro method), are turning yellowish - the leaves…?

My PH level is 6.

Here is some information to help in your review and comments regarding the yellowing of the leaves.

Hydro grow system
Light on for 18 hours, is this too long?
Temp 72-77
Humidity 45%
CO2 booster (adjusted to high yesterday)
Thrive Alive B-1, red, per instructions (mixed with water - distilled), added weekly for 3 weeks with all new water
Water level just below grow cups
PH 6
Light 48 inches above top of plants
Small fan on low

I’m a first time gardener, and perhaps I don’t understand:

At what point are the plants in vegetative stage? Age in weeks from sprouting, a certain height and/or a certain root structure/growth?


#2

tho the water level sounds low enough, the rock wool the babies are in looks too moist.
that has to be fixed.

the veg stage starts when the fourth set of real leaves are growing in.
the first two rounded leaves are called cotyledons, they feed the baby.
the next set of leaves, real marijuana leaves are set 1.


#3

put some hydroton in your net pots and try to reduce light getting to your nutrient solution several issues right of the hop water should be 3/4" lower than net pots max light is getting right at your root zone you also didn’t mention the ppm of nutes.
Res temp is important too with light getting into res soaking wet rockwool you have breeding ground for root rot the yellowing is because they are getting too much moisture. When I said 3/4" that is the highest water level you could safely be 1-1 1/2"