White widow autoflower, in 5 gal pot, foxfarms soil, one led grow light about 6 inches above plant, temperature stays between 74 to 79 degrees. Started it in a small yeti pot first.
Sometimes they grow fast and it takes a day for the chlorophyll to darken the leaves. I wouldn’t worry yet. Which Fox Farm soil is it? It looks nice and healthy.
Are you checking the pH of your water?
Possibly causes of top growth turning yellow in seedling stage can be light too close. Raise that light up about 10” May help.
Also, watering next to the stem will drown them and cause them to turn yellow. Water in a diameter about 3”out from the stem. It will encourage the roots to reach out and search for the water making the plant stronger.
Good luck and keep’em growing!
My guess is over watered.
what wattage and intensity is this light? Looks like light burn to me