Issues with northern lights auto seedling

Hi, this is my first post on this forum as well as my first grow and I am currently having issues with my seedling. To start the plant is 12 days old I have only been giving it plain dechlorinated water and natural sunlight since its juat a seedling. I started noticing the cotyledons were looking burnt so I just kept watering as I made the mistake of planting straight into back to the roots organic potting mix thinking the potting soil mightve been too hot for the baby plant. After 2 days the cotyldons fell completly off and the yellowing spread to the first set of true leaves and it spread rapidly and has now spread to the second set of leaves. I water every 4-5 days since the soil does not drain well and I wait for the surface of the soil to dry she also get about 12 hours of sunlight a day. I water around the plant as well to help the roots grow. I'm a newbie but im suspecting the plant is cannabilizing the lower leaves as the lower leaves always look worse and spreads to the newer growth. I'm looking to utilize a better medium like coco next run and making my own mix. Thanks in advance!

thats a potting mix????? the nitrogen bacteria will be digesting the wood and not be very available to the plant for growth

anyhoo, if it were me, i would get a bag of ordinary potting compost, dig or scoup that plant out and wash off the soil from the roots and repot it in the new potting compost.

again, my opinion, but start by learning how to grow in the soils available, then after a few plants, then concider mixing your own soil.

yea it is. After studying up on soil I was like man I just bought organic mulch lol. I'm gonna try and re pot it in better potting soil like u said, but you said you think the nitrogen isnt available to the plant couldnt I just feed it? Only asking because i want to learn how plant feding works. I thought microbes breaking down organic matter would make it too available for the seedling and burn it. Thanks a lot for your reply.