Brown black spots yellowing edges

I'm in veg. got a few babys&Moms, they are browning from the centers to the outside. It starts at the veins it starts spotty and gets worseThere is a lot of new growth and only some seem to be suffering. I did see a couple little black spots too checked them out not mites. It is mostly adult older veg., please help I will try to get photos up please help. Oh and some leaves are yellowing too I'm under 2 1ooo hortilux metal halide with plenty of room oh and I'm arond 75-82 degrees 24 hour light regimn

sounds like an mg problem. if the browning was on the edges more likely potassium, but mg deficiencies are pretty common. can be fixed using epsom salts