Yellow spots are due to a lighting issue, leaves too close. These look very insignificant. So no worries. Don't let them get any larger. Also try spacing them a little bit further away.
As for the gray spots it could be a mineral deficiancy, more than likely magnesium. Try 1 tsp of epsom salt in a gallon of water and apply to plants sparingly.
Could be disease.
Could be cannabis strains. Need some more info on plant...
Thanks man, PurpFreshy