Cal/mag maybe?

You have cal/mag in the micro bottle which should be enough once you switch your ratio to the "Early growth". I use cal/mag in my grows as a buffer in the water to help keep the PH more stable( it takes a lot of cal/mag to get a toxicity ) So if you have some it wouldn't do any harm to add it. My guess is that is abrasion damage from the leaf hitting the net pot and is nothing to worry about. General hydroponics light feed you should be at: ( Always add micro FIRST ) Micro = 0.95 ml/l or 3.6 ml/gal Gro =0.9 ml/l or 3.4 ml/gal Bloom = 0.69 ml/l or 2.6 ml/gal Happy Growing