Deficiency? Calmag?

So, just curious if this may be a deficiency, an environment problem, or maybe nothing to worry about? A little spotting on lower leaves , and this one leaf is turning fairly yellow. Modular ebb and flow in hydroton. All 12 plants seem to have this light spotting on lower leaves. Using advance nutrients coco Sensi grow a+b with voodoo juice and b-52. Overall growth seems fine and plants seem happy.