Is this calcium deficiency?

could be. the fact it's so close to the veins in nearly all spots is a bit weird. If you don't have any ocd watering habits, i'd raise the Ca portion of fertilizer a bit while keeping other stuff unchanged as much as possible. Also looks slightly overfed on N, too, which will quickly turn into just plain overfed, if you continue at current rate of application. So, a bit more Ca, bit less N would be ideal. It would take weeks to see impact of N. Ca should at the least slow down any progression of those spots.. . if they speed up in progression beyond the next day or two, that is not Ca ppm related. Necrotic spots don't heal, so just getting fewer would be the initial sign of the "right" diagnosis. Without more info, and even with more info, diagnosis is often a guess.