spotted leaves

im not sure whats going on here but ive been searching for 2 days and still not sure what the problem is on 1 of my plants i have some leaves that are getting little rust spots and the middle of the leaves r kinda getting a lighter color
it is in fox farms ocean forest she is about 35 days old water with my tap water that sits atleast a day ive given 2 waterings about a week apart with half dose ff grow big(1 teaspoon) + full dose grow big (2 tablespoons) under 400 hps 18/6 light sch. about 81-82 degrees day and between 70 -75 at night ive include a couple pics of whole plant she is looking healthy nice and perky im thinking a cal/mg problem not sure though

does look like more of a cal than mag def but could be both, I have heard others having late issues with cal/mag def's using FFOF soil

what would be a good way to fix it ? lime or epsom salts?

anybody there??