Seedlings dieing

Less water start in clone cubes on heat pad enclosed holding moisture… water daily keeping moist not wet… move clone cub to dirt cover water some and light 24 hours for 5-10 days then 18/6

If you plant directly in something like a all-mix ore a amended super-soil in a big container (as you would do with auto flowers) you should put a hand full of a light fertilized soil ore some kind of seeding soil in the middle and plant there. Too much fertilizer ore microbial life can be dangerous and potentially deadly for that little seedling. Sorry to see that, dont get demotivated. Good luck, High Mountain Gardening

Its soil, but i see no perlite, plus its heavily preloaded and enriched by you, any small delay to water and plant roots burn heavy in such young and sensitive times .. My thoughts....

Coco/perlite at 70/30 Plant half inch deep and slightly cover. Mist coco until damp. 2 or 3 times a day. Don't allow it to dry much during first week. Don't drown the thing though. The less perlite you have the more water retention the coco has so be careful over over watering. This is why we normally just use a spray bottle and mist it with 5 or 6 sprays 2 or 3 times a day. This method is tried and true. If done correctly and with ample lighting the plant will grow. Unless it's just shit genetics. Heard good things about barney's farm, but never grew it myself. Sorry for your loss Goodluck on your next grow.

Looks like too much water. You need a 30 percent perlite for air and drainage.

hard to tell from the pic but might be dampening off, a issue with seedlings where a fungi/mould gets into the base of the stem and causes it to collapse and rot then die, you will notice the base of the plant looks like its squished or collapsed and brown/black vs the top half looks normal. It could also be from the medium and its just not supportive of seedlings. If it to hot they can just die as the new roots get burnt and then it can't take up water. Can aim for a different medium mix next time. Good Luck!

Autoflowers suck, don't grow them?