Help...Do you know what this is ???

Hey y'all,
Going into week 5 noticed small yellow dotting on 2 bottom fan leaves. (pic included) I'm unsure whether or not it's over/under watering, nitrogen deficiency... Maaaaaybe spider mites? Used magnifying glass didn't see bugs nor is it on any other leaf or plants. So 1 of 6 in the same grow room.

Thanks in advance to all the help!

Can you snap a photo without the LED light? Could be a couple things. That's a common problem with mites, could be start of powder mildew fungus.