DWC, seedling deficiency

Hi there guys,
First time in hydro and dwc and i'm having problem with one of my plants which is turning yellow, I'm not sure what can be the cause of that, because I have the same setup for another 3 plants and they are growing great.
They are 4 days old.
I'm using hesi nutrients and following this table .
I'm using 5 gallons pots and PH moves around 5,6 to 6 between days until I adjust it again to 5,6. EC is 1,2, water temperature is around 22°C and 22,5°C, environment temperature is 26°c and I'm using 6w air pumps for each pot. I check all the variables like thrice a day.

I'm not sure which could be the problem because 3 of them looking great but one which seems to grow slower.

any advice would be great.

Some times the roots aren't out of the net pots that young and they'll ha e problems. they almost always bounce back but by then your others are huge. next time, start in coco, like a waxie cups worth and let your plant get some decent roots first.

Airwalker16 said:

Some times the roots aren't out of the net pots that young and they'll ha e problems. they almost always bounce back but by then your others are huge. next time, start in coco, like a waxie cups worth and let your plant get some decent roots first.

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I realized that before yesterday, because others had huge roots and this one have not shown anything, So I decided to add more nutrient solution in order to the water solution get higher and she started to recover, now is showing her roots out of the pot and she had recovered her green color and started growing again. Well if this have not happened now, it will happened to me eventually, so I'm glad that happened on my first try and just with only one.
Thanks u very much :3