Looks like a calmag problem to me its hard to tell though so your gonna either have to start adding calmag or wait until it gets worse to know forsure. Nitrogen looks good cause the plants green, could be ph but i dont really believe ph causes marks on leaves, everyone else seems to (newbs) but ph being off is supposed to cause certain nutrients from being taken up so if the ph is off its still,a,nutrien issue. Meh, you should be able to tell in a couple days.