I never worry about strange spots at this age.
If I see any, I will give them a close look for any thrips or thrip larvae and give the leaves a light rub between my fingers to be sure (even very small larvae cannot tolerate a finger over their back)
Otherwise those spots are just as likely to splash burns as anything.
At a week out of seed, the nutrient needs are very slight, almost any amount of Calcium or magnesium should bee fine.
And as far as I am concerned, if a person is having regular "calmag" problems, they need a new nutrient line regardless of what lights they are using and what strain they are growing.