Seedlings are yellowing - need help!

Hi, can anyone please help identifying what is causing my seedlings to turn yellow?
#1 is 23 days since planting germinated seed.
#2-4 are 10 days and starting to show the same signs.

#1 started to yellow and curl down after 10 days and growth has slowed dramatically.
I started with 0.5l and transplanted #1 to 6.5l container but it’s been a few days and I’m not seeing any improvement.

more info:
60x60x160cm grow tent.
250w hps dual spectrum with reflector 2ft above seedlings.
S&p TD-250 Exhaust fan.
Clip fan for air circulation.
Humidifier keeps 70% during lights off and 50% during lights on.
Temps are between 23c-27c.
Light cycle is 18-6.
Watering about 60ml every 2 or 3 days. Tap water. Ph meter is on the way!
I have a bottle of organic nutrients which I haven’t used yet.
Using perlite soil.

Is there anything i can do to help my babies?

They look to be in shock. How often are you watering them and how much?

I’m not familiar with how high HPS should be off seedlings but 24” seems really close for them to me. I keep an HLG-65 LED that high off my seedlings.

G.I.JOSE said:

They look to be in shock. How often are you watering them and how much?

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I'm watering 60ml (shot glass) each, every 2-3 days. Is that not enough?

TreeFarmerCharlie said:

I’m not familiar with how high HPS should be off seedlings but 24” seems really close for them to me. I keep an HLG-65 LED that high off my seedlings.

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I was thinking about turning off the light for 24hrs and see if they’ll snap out of it.

Is your medium coco and just added perlite? Soil needs to be damp consistently, they are starving imo.

freemancat said:

Is your medium coco and just added perlite? Soil needs to be damp consistently, they are starving imo.

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I’m using coco-perlite mix bag from the local hydro shop.
Are they starving for more water?

Hitboy said:

I’m using coco-perlite mix bag from the local hydro shop.
Are they starving for more water?

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Yeah coco should never get dry, that and they need to be fed something soon. Start off with a diluted solution.

freemancat said:

Yeah coco should never get dry, that and they need to be fed something soon. Start off with a diluted solution.

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thanks
Hope to get some growth in there soon.

Watered all of them today with feeding solution.
I didn’t mention originally that seedling #1 has brown spots between the veins of the leaves.
Also, didn’t buffer the coco mix with Cal\Mag And i don't have any ph kit yet.

Will it help if i order a Cal\Mag supplement?
what can i do until it gets here?

Probably time for a little fertilizer. I'd put a small amount of it, like really small, in water, however much it says to use like one gallon or liter, and water the entire soil so it's all wet. Let it dry out some before next water. The cots are supposed to go yellow, the rounded leaf looking things. If you haven't given fert yet I'm thinking it's time for a small dose.

polishpollack said:

Probably time for a little fertilizer. I'd put a small amount of it, like really small, in water, however much it says to use like one gallon or liter, and water the entire soil so it's all wet. Let it dry out some before next water. The cots are supposed to go yellow, the rounded leaf looking things. If you haven't given fert yet I'm thinking it's time for a small dose.

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Thanks
gave them half of the chart dose today.

You don't always have to give the fert every watering. As they get bigger and you maybe you transplant to a bigger pot, you can give a little more. Just remember it's easier to add more later than try to remove it if you give too much so go easy.

Really appreciate your help!
Here are some pics that i just took:
Still they are relatively small but i planted some more seeds and hopefully they will catch up as I'm starting to understand this coco stuff.