Help my seedlings

Looks like your growing in coir. Coir is a soilless medium and void of most nutrients. If its unbuffered it will steal the Mg and Ca in the feed and release extra K and Na. In Short you need to be feeding from Day one when growing in Coir or Peat if they are not fortified or have some form of slow release nutrients. They are hungry and have nothing to eat. It would also not hurt to add in some aeration to the medium via Perlte or Vermiculite.

Hey 👋 I see two issues. First is the soil as mentioned below. Your plants got 0,00 nutes, so they are very hungry. Second issue is your watering. Soil looks extremely dry, especially for coco. Water them with grow fertilizer and hope they come back to life again.

That plain coco is your problem. You would be much better mixed with perlite and or clay pebbles.. coco is inert meaning ot has no nutrient value at all.. make a better mix amd add small amout of nutrients... Good luck

Set your light to proper ppfd, which is 150-200 at this stage. Coco in combo with led lights requires more CaMg, so add this one too as a preventive manner. Make sure you oversaturate the medium with water. Feeding solution must be set to 6.3 in order to get the good stuff available for the healthy plant development. Good luck ✌️

Looks like they are in plain coco. Just coco alone has 0 nutrients. When your not using a good soil you need to add amendments or start liquid nutrients off rip

More water

OMG it's like they in the desert - set ur led for 10-15k lux and set timer for 24h - flush and feed em with 100-150 ppm feed (NPK ratio 2:0.5:1) don't use any calmag fert - cover em with plastic bag or cup

is that pure coco? Need some drainage/aeration improving amendment in there next time. Not the cause of yellow plants. Re-assess color with normal lighting. Grow lights make things look more pale than they really are. pictures are too blurry to be certain, but looks like node spacing is slightly tight, but not crazy - sign of too much light which can cause paling. Allow node spacing to guide adjusting light intensity... shouldn't be too stretchy, nor stacking nodes super tight. When leaves physically push other leaves above them causing them to angle upward is a sign of extremely tight nodes. Leaves (alternating axis) originating from roughly the same vertical point on stem is too tight... Is this coco coir? This needs to be fertilized every single irrigation. The first 7-10 days a seedling is packed with enough nutrition, but it needs nutes from medium or fertilzer soon enough. Can't grow without building blocks. 1) fully saturate. If this is soilles, also get 10% runoff religiously and fertigate each time. 2) wait for top layer to change color and repeat. With coco you can do this a bit sooner, but early on i'd have a more exaggerated wet-dry cycle to promote greater root growth. A good wet-dry cycle also reduces root zone problem risks. the runoff is incredibly important in soilless growing. it maintains the equilibrium that results from fertigation and prevents buildup. you can still choose to feed to much and that may need adjustment, but any symptoms you see are never caused by buildup in medium if religious about 10% runoff. One less thing to worry about while you adjust your formula(s) to work nearly flawlessly for each stage of life cycle. It's a reasonable goal to have and you can get there very fast compared to soil methods.

I would suggest you go for a light soil mix and some easy to use 3 part nutrients for an easy grow. Growing in coco especially directly planting the sapling into coco can be tricky