Stalled Seedlings Yellow Tips - Soil

Hi all. First time posting long time member. Having an issue with my 10-12 day old seedlings. It seems like growth has just stopped and my leaf tips are turning yellowish. I have been watering mostly tap water or distilled water, PHd down to around 6.3-6.5. I am using just Kellogs organic Outdoor Potting mix with no amendments. I am watering when the medium is dry to the touch and the cup is lighter. Not certain about overwatering but that would be more likely than underwaterering. I did notice soil runoff was around 7.4-7.5. Rh is good around 50-65% and temps from 70-85 depending on time of day. Using 300w mars led in a 2x2 tent with one small fan blowing air around. I don't want to change too much too quickly if someone can spot the issue with my babies. Any clues or tips to get them back on track? I have not fed any nurtients up to this point.
Tap water reads about 079 on EC pen. Ph water in low 6s. Soil ph is questionable as is the accuracy of my pen. Please help! Thanks

I should also add that lights are about 18 inches for seedlings. Strains are red poison/bloody skunk autos and blueberry haze autos. I have a light schedule of 18 on 6 hours off. The seedlings have now been the same size a few days now even though the new leaves seem to be forming, the lower leaves have always been curled under as picture shows. Thanks in advance.

I wouldn't worry about the little cotyledons curling under. They fall off after the main growth tip takes off anyways. The serrated leaves are now gulping what the lights are giving them.

And at 18", the light you are giving them might be a tad intense for their small size. I keep my blurples 24" - 30" above seedlings and clones until I see that the growth tips are coming along and the nodes are forming. Once they show good growth, I gradually drop the lights to 18"

No sense in ph-big your water if you are growing in organic soil. Ph testing your water and/or runoff tells you nothing useful. You need a pricey soil probe to check the actual ph in the root zone with accuracy.
The soil mix just seems a bit heavy to me & bad drainage could be the cause. You could be underwatering yet without good aeration in a heavy outdoor mix the roots are not getting enough O2. Roots need to breathe. I would poke some extra holes in the bottom & sides of those cups for now. Just add in some perlite and/or coco to help lighten up the mix when you pot up next time. Adding in some worm castings helps green them without harsh nutrients.

What @StareCase said. Raise the light to 30”. Leave it there unless the thing starts to stretch. Do not overwater.

Thank you guys. So to get these babies back on track you would poke holes in the cup for more aeration, do not water until needed, and can I add worm castings to the solo cup or should I look at transplanting them into new soil? They look a tad more yellow on the tips today and still not much growth today. I may look into getting some FFOF /Happy Frog for my next seedlings (currently germinating blue dream and green crack).

Thanks again for the help! Almost don't want to touch them afraid they will die lol.

Updated pictures today. Tips more yellow. Not adding any water. Have lights about 28 inches from plants.

The other plant

They look fine for the most part. There doesn't seem to be much in that potting mix. Maybe try a light feeding?

What are you using for micros?

Those leaves with the yellowing are also some of the first leaves to appear. They just get the plant going. Those leaves will also be some of the first leaves to be cast off by the plant.

The second set, those smaller leaves in the middle that will comprise the growth tip, look good. Give it another couple of days and see what those littler leaves look like.

Have not fed these girls anything but tap and distilled water (tap water just to get some calcium and mag naturally). It's hard because they are the same size as they were at 6 days and it has been about 12 days now so I'm weary of feeding them on a real schedule. I'm wondering if I could transplant them into a slightly larger square pot after saturating the rootball in fresh water and put them into some fox farm - thoughts? I want to keep things as organic as possible especially with them showing some sort of stress. Thanks so much for the tips so far! Will take all I can get.

Quick update for those following. I gently transplanted these into FFOF. Was surprised to see there really was no root ball just one tap root. Used some Mycor to hopefully help prevent shock. Tips and lower leaves still getting more yellow, no clue if they are on the way up or on the way out lol. No new growth. Used correct ph water and a little compost tea that our local hydro shop had on hand to help with the transplant activities since they needed to be fed anyway. This is obviously my first grow and these were more of a trial. If they pull thru this I will be incredibly surprised because I have broken all the rules so far lol. Feel free to chime in with thoughts!

Other plant

Just a quick update. Plants stalled a bit after transplant and one of them is still slow, but check out the big one! I can't believe they recovered from that. So lessons learned here so far - don't use a thick/heavy soil medium made for outdoor plants without some sort of amendment to make it more airy like perlite or vermiculite. This was a very barky mix. Also, drainage was not great so it was likely suffocating in the solo cup and root growth was very minimal. What my plants seemed to like - new home in fox farm ocean forest, with good phd water and same exact light schedule. I also believe my growing area was getting too hot and not enough fresh air exchanged, so until I get proper exhaust I have been opening grow area up and adding more fans as well as outside time for plants. Slow but steady - these are autos and because they are still pretty small right now, I'll be interested to see when they start to flower. All an experiment! New growth looks great and just fed both of these babies nutes for the first time yesterday since they are just midgets but actually like 2 or more weeks old, I lost track of their age lol. Cheers.