White spot

Shit... powder? Keep the leaves dry. Could just be a little midlew.. wipe it off very very gently... keep it dryer on leaves... make sure top bit of soil gets dry to touch before watering. Do not foliar spray... it's just stupid, stupid, stupid to do without a cause (like a pest or something is a good reason.. if that mildew spreads, maybe a good reason -- if it is mildew). Just looks like a pale spot in leaf on picture... so, if it doesn't rub off, it isn't microbial growth and really is nothign to worry about... if it is powdery -- stil happens nearly every grow, but on a younger plant it's a bit more of a concern or if it is all over as opposed to 1 isolated leaf that was overlapped and touching another one creating the environemnt for the microbial to grow with additional moisture and shade.

If it were the light, the sprout most likely would have fallen over in an effort to reduce light hitting it. So, you can rule that out for now. That's a cotyledon.. sometiems they come out tarded... no worries. Same with first 2-3 sets of leaves... be more forgiving on asthetics... if a spot expands or gets worse, then you can worry a bit more. initial leaves aren't even symetrical in many cases... and they turn out beautifully later... no worries, really.