17 day old seedlings - suffering leaf burn / curling

[ToughCall]

Heyo,

Need some help. I recently transplanted some young seedlings and now they are looking worse than before.
I used an ec pen when I added nutrition, kept it at 212ppm.
Soil is 3 parts Happy Frog, 1 part Lite Warrior.

Light is 18/6, using spider farmer's SP4000
about 28" from top of soil. Lighting is on during day hours, 7am to 1am. Tent is a 4x4x6.5

Temp swings are my biggest challenge still, but between 65F to 84F.
Humidity is 44%. Started today using 6" fresh air intake and 8" exhaust.
The intake exhaust is lowering temps and humidity.

Thinking of using timer to schedule intake/exhaust from 7am to 7pm schedule. Nights are still too cold and they're very young.

Lastly, water is RO, and just read about RO not having calcium or magnesium.

I have all my equipment finally, but dialing it in has been a hot mess.

Not sure if pics assist in determining issue. But would sure appreciate the advice.

Thanks,

[RASTA]

Was it just growing in a wee jiffy pellet or suhin before?
It kinda looks fried, a know not a lot about that soil u using, but might be too hot for that size plant.
How often are you watering them?

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[ToughCall]

Rasta,

Germinated in paper towel and baggie. Put 3 in solo cups and 3 in jiffy pots. 2 to 3 days for watering and using liquid seaweed, molasses, and URB. 212ppm. About 30" from the spider farmer SP4000 led.

[redisiel]

They certainly don’t need any feed at this stage mate. And your better using tap water left out for 24 hours before using it.
Hope this helps a bit for now, also be careful not to overwater
Atb
Redz

[ToughCall]

redisiel,

So RO just complicates it? Having to add calmag etc.?

Tap left out 24 hrs is a cheaper simpler option.

Any thoughts about my intake/exhaust issue? Running only day hours and off at dusk as it's still too cold?

[M_C]

Overfed.......

[Herbitual]

Pic #1 is definitely too wet, TC. The soil should be nothing more than moist...like when it comes out of the bag - that's what you should be aiming for.

Do you know anything about your tap water in terms of hard/soft?

Mine, for example, is very soft resulting in a low EC (<0.2) which means, in short, it doesn't have huge quantities of calcium and magnesium (plus other minerals). My calcium level from the tap is something like 6x less than a healthy plant requires so I have a bit of a battle there. RO would take that to the ultimate degree.

IMO, even low EC tap water left out overnight and used in soil and you'd be fine for a good 4 weeks before you need to feed.

Again, just my opinion, but RO is a complication too far before you know what you're dealing with straight from the tap.

[Herbitual]

Just looked up both soils you're using.

You definitely should not, without question, be feeding your seedlings in that mix this early in their life.

I'd almost say it was too hot even without additional nutrients being given.

[Herbitual]

Also, if that is genuinely your temperature range, then that is not a challenge at all. That's fine.

However, your intake should be 24 hours. Just switch the schedule around so the 6 hours of darkness is in the middle of the day.

[Herbitual]

And having completely missed Redz post (sorry, mate) he says everything but in far fewer words.