Any ideas on what could casue just this one to yellow?

Might need some watered down nutes.
However like every thread here you are going to need to provide more information.

What growing medium are you using?
What kind of plant are we looking at, photo or auto?
Light set up, as your lights could be too low as well, for the plants size.
What nutes are you currently feeding/watering with and strengths?

It’s just so you can get the best information possible from the longer term growers and those that have worked with cannabis awhile if not decades.

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I would pull
Light back to 24” during much of veg. QBs can have hot spots directly in the middle. If it’s in a good soil and isn’t dry or overwatered, the light would be my thoughts but it might be time for some additional grow nutes. Maybe a good tea. Don’t forget to supplement your sugars a bit as the mycorrhizae network spreads throughout the soil. I use a bit of molasses twice a week in those early veg weeks. But again I grow in a mostly coco medium so I’m giving nutes from day one, albeit watered down dependent on age. Once the mycorrhizae network is set up it will bring nutrients that aren’t readily bioavailable right to you plants growing root network. Your PK is quite important now for building and strengthening your root network besides working with the N to darken leaves and Calcium to go with the Carbon to keep up that fast growing plant.

It will work out well.


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