Yeallow stripes 3rd week of flower

If the yellow is from bottom up it is lack of nitrogen, but if its yellow across canopy starting at edges going inward on leaves, It is probably light burn. Light being too close or bright. From my experiences. Hopefully this helps. Cal mag deficiencies from my experience has been small brown spots on leaves. Honestly I think you are looking fine from pictures. Hap po y growing.

You can test the ec and ph of the soil... You should know this already if you’ve done any research into watering. Water with runoff and a good amount, at least 30% imo, and measure the ph and EC of the runoff. Will give you the closest idea of the state of the medium

Early yellowing of leaves is a nitrogen problem. Maybe underfed a little, maybe some lockout do to excess nutes in the medium or ph is going out of whack. Check your runoff ph and ec levels, if ph is high or low fix if ec is to low add more nute, to high then run some ph water to bring it back to acceptable levels. Cheers