Cotyledon leaf turning yellow

Medium: Peat Pellet in Pro-Mix
Water: pH balanced spritz in dome
Lights: LED 100W 9" from plant
Since Germinated: 13 Days
Seedling: 6 days

Noticed today a yellow spot on the cotyledon leaf, not sure if it’s a watering issue or light.

Anyone have any suggestions?


You are currently in a nutrient free medium. The cotyledons store onboard nutrients for the emerging seedling to consume. Once they have started to die you can start your nutrient schedule.

This is entirely normal and expected.


@Myfriendis410 is absolutely right @SmokingWolverine


I saw this post @Myfriendis410, and as we have discussed that I am switching to Pro-Mix HP, when to start feeding was a top of list question for me. If I am reading this correctly, once I see her cotyledons beginning to yellow slightly, I’ll start with a light nute (Advanced Nutrients) schedule. Am I correct to think this should typically be around the 2 week point (from emergence) with most strains?

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2 or 3 weeks is about right. Start with a very low dose like 1/4 strength or around 400 ppm for a couple of weeks before bumping up. You should never need to be above 800 to 900 ppm during veg and 1,200 to 1,300 in mid flower.

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Again, thank you for the good information. I just mixed up a batch of AN nutes to feed the 6.5 week auto this afternoon when her lights come back on. Keeping lights off (18/6) during the heat of the afternoon.

She is an auto so her buds are stacking up quickly now. I tested the ppm of the nutes and supplements after mixing and read 1100 which is really close to what you said to target during flower. I’m not going full strength per the schedule AN calls for, so maybe I am 70% now as I started real light and slowly getting a bit stronger. Sometimes less is more as they say.

I read the ph of the nutes to be 6.0 so I upped it a bit to 7.0. They say with ph perfect technology in RO water I don’t really need to fuss over the ph, but old habits die hard. I think she’s dialed in pretty well now that her organic nutes for the OF have calmed down some.

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