Yellowing

Its my first grow indoors i used nector for the gods soil, started all of them by seeds they are about a week old, i sprayed them twice, watered with mammoth p and the rest has been feeding with water. They look great and are growing nicely, but they have just recently started showing yellow spots. Everything i find says leaf septoria but im not sure, any help would be much appreciated thanx.

Is it Nutrients burn or cal/mag ?? What kind of soil is it ?? Need pics for a better answer