I would check the medium. The plant is pretty small to be showing signs of a deficiency to that degree. Did the medium come pre-loaded with nutrients, like Fox Farms does? Too much of certain nutrients can cause issues with other nutrients not being available for the roots to take them up.
Cal-Mag, everyone's cure all, can cause serious magnesium deficiencies if used too much, especially with neutral or slightly alkaline soils. Too much P or K can also interfere with the absorption of other nutrients.
Depending on the amount of fertilizer/nutes in the soil, I would think it might be overfeeding, causing deficiencies. In my experience over the last 30 years, I haven't seen a case of nutrient deficiency unless it was in a water based system, or a growth medium that has been used up and not replenished … and even then it was minimal. Just about every case was due to overfeeding, when people confuse the nutritional requirements of a 10 inch plant with that of a 7 ft tall plant. Plants, like people, don't really benefit from overfeeding, although people keep growing when they are overfed! Keep up the good work!
I do water once every 3 days since the season it's pretty rainy, btw didn't fertilized them at all (that's why the nitrogen deficiency came on) just gave them micronutrients, 2 ml/lt
