I would always use Cal-Mag Plus 3ml veg, 5ml per gal Flower. That one leaf looks like it's from External damage. The rest of your plant(s) look great! Careful on that back one possibly looks like its starting to get too many nutrients being from the clawed leaves, nutrient solution for soil should be 6.2. Use 75% strength, and water pattern do N/N/RO (Nutrients, Straight RO. So every 3rd watering will be straight RO)