Nute burn or Nute deff.?

[timetrial]

Ok, so i know that a really common problem encountered while growing is nute burn or over fertilizing. I believe that I am encountering that problem now. However, how do i know for sure whether it is nute burn or nute defficiency? Both seem to have similar symptoms. Its obvious to tell b/c you can just look back and see if you've given it ferts or not. But I didn't fert my plant for about a week and a half (then the leaves started showing some yellowing so i thought it was nute deff.)and when I went back to the ferts the leaves really started yellowing and dying. The plant was loving the nutes up until the fertilizer break and now it seems to really be suffering. What's the deal?

[SmknVTEC]

How old are these plants?
What type of lights you using?
What type of soil you in?
Check the ph of your soil.
Post some pics if you can.
Usually N deficiency starts with yellowing and moves up the plant. Over fert starts with yellowing and brown necrotic patches on the leaves.

[timetrial]

we had a ph problem for a little while but that was corrected. The plant is about 6 weeks old and just started on the 12/12 cycle. It is under a 250 hps and in miracle grow organic soil. I do believe now that it is burn b/c there are some brown spots on the leaves.