Can anyone identify this problem please?

Im currently on day 35 of my first grow and have had problems with one plant for a couple of weeks. I am getting yellowing, crispy leaves with brown spots on the older bigger leaves of the plant. Details of my setup are in my previous post and im happy to give more details if needed but i was just wondering if anyone can identify the problem from the pics at first glance.

im guessing its either an under or over nuting problem, although im not sure what to do..

would really appriciate some input. Thanks

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Looks like pretty classic nute burn. Hard to tell without more info. Find the help form in my signature. Cut and past answers here.