brown spots between the veins

[Frank]

Hey Ron,
Thanks for all the help so far. I am having a problem with my plants developing brown spots between the veins of the leaves. It started on some of the bottom fan leaves, now it's becoming more and more uniform. I am guessing a (Mg) deficiency but it could also be iron. Please answer asap I lost 8 of 10 plants to an earlier over fertilization episode. She is my last hope. I think the other one is a he and will have to be terminated.
Thanks bro,
Frank

[Ron]

The only sure way to correct fertilizer problems is to dump your tank and start over. Just because your ppm is correct doesn't mean that all the elements in your solution are correct.