Help Diagnose Spots

Does anyone know what the brown/blackish spot are on my new plant. I have 3 others in the same DWC that aren't showing these spots.

Conditions:

Temps: 72-75
Res Temps: 67-70
PH: 6.7
PPM: 240-270

nothing?? Anybody???

I had something similar during the seedling stage with my current plants... Had them in perlite and spagnum peat moss. I think its a def, i'd up the nutes to 1/4 str or seedling str.

Notice the one of the cotlyedons in your first pic? It looks like its eating itself already.