To sm & dark to see, but going by what you said, my guess would be nute burn. Dont feed seedlings untill they've put out a few sets of leaves. When they start growing fast is when they need feed. Untill then, those baby roots can burn, showing the symptoms in the leaves. When the growth rate picks up, they're telling you they now actually have a root system, instead of just that seedling tap root. ~~~ PEACE! ~~~


P.S. The roots are no where near the bottom, so that's not the problem. The salts are draw to the top of soil through evaporation. When soil goes bad on the bottom, its because its been kept too wet & sours (stagnates).