Upper leaves are yellow

A question from a fellow grower:

I have an AK47 auto(genetics from ILGM) growing under 20/4 CFL , soil PH 5-6, but I don’t know why the upper leaves are yellow. I also add extra Iron but no change.
I have attach a photo of my setup.

Looks like nitrogen deficiency from over watering. If so you only need to.cut back on watering. But let’s see what Stoner and Latewood have to say. But till then how much have you watered your plant.
Also go to Beginner FAQ and fill out a support ticket this will help in solving problem.

B Safe

I agree with garrigan on this. Although if your ph is more of a 5 than a 6 that could be a contributor as well. Also, Im not sure what you meant by 20x4 cfl. Is that 4 bulbs each a 20 watt? Are those cfl watts or equivalent watts? If they are all true 20 watts then you could probably take one down for the time being as 80 cfl watts is more than a seedling needs. Good luck and wait for the experts.

thanks for your reply. so the 20/4 CFL. i mean 20hr day and 4hr night. the CFL am using is 85W.
I water the plants every 7 days.
The temperature is about 24 deg. C

Well I doubt that water once a week is too much for your small pot, so maybe focus on the ph and keep that between 6.0 and 6.5. Maybe even switch to a 16/8 time table until it has more sets of leaves and a healthier growth pattern. I
personally think giving the plants a good rest period, (especially at a young age,) can be very beneficial.

I agree, now that we know for sure that it wasn’ tfrom over watering.
We now can focus on the ph as groovin has stated.

The soil what kind and list any nutrients it may have in it.
This also may be the problem.

B Safe

On soil bag its written ; contains coir, composted organics, horticultural sand, loam and organic fertilizer.
For nutrients I use “Vilmorin- engrais Tomatoes et potager du balcon”-
h t t p://côtéjardin.com/epages/box25283.mobile/?ObjectPath=/Shops/box25283/Products/%22EngraisTomates+Liquide%22&Locale=fr_FR