Could be a ton of things.. sorry.. but need to know what lighting you use since it could be light burn ..
Do you use any nutrients? .. could be nutrient burn
What soil is it in? Could be hot soil heavy in nutrients right out the bag.. amazing.. but sometimes overwhelming for new seedlings..
Those white specs are not bugs are they? Just making sure on that as well..
Dont think over watering because no leaves are curling or clawwed..
Maybe under watering but doubtful at such an early stage.
I know your intent was someone to see the plant and say " hey thats nitrogen deficiency " or something like that.. but the problem with plants.. is ALOT of the problems, deficiencies, excesses, etc.. all have extremely similar looks to them ..
So without pretty specific information.. like lighting, watering routine, medium, temperature in area usually, nutrients.. it will be hard to give a definative answer.. and more than likely shots in the dark.
Just trying to help.. since i actually had problems with one of my babies a few weeks ago... and prior to giving more specifics on her routine.. i got literally 4 different possibilities.. and all did in fact look same ( nute burn, over watering, triphs, root rot) ..
If we can figure it out she will rebound fine tho! My plant is much better now!! Heres her i think 2 weeks ago and now! Blurple is now .

Were the leaves touching the soil?

^^^^^
My wife has something like that from idk.. soil decay? On some of her strawberry plants leaves that just layed in the soil.. may very well be it.

Overwatered