@Ti_BR, Well, at this point in my grow, the soil was the depleted of nutrients, so it was generally deficient in nutrients. But yes, older yellow leaves could be because of a mag deficiency or a nitrogen deficiency. Also, og's can be very finicky so you have to watch out for odd growths, odd nutrient requirements, and can herm easy if the genetics aren't strong but as long as you are consistent with your sop's u should be good.
Happy growing!