Burnt Tips, dont know what it is!

I woke up the other day to find that the tips of my blue widow have been burnt . I have checked the diagnosis pages (sounds like a doctor lol) and the ones it seems to be most likely are Boron, Magnesium, or Iron deficiency. Can anyone help a new grower out? I am using 4 23W cfl's, Schultz flowering nutes (10-10-4)
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GAWWD am I an idiot, It looks more like a potassium deficiency, esp looking at my nutes....I could actually feel a lightbulb light up in my head when I realized it haha

Be careful, the first sign of overfert, is burnt leaf tips, and although your leaves aren't curling down, it may be coming soon. Right now would be a good time to flush, get the PH where you want it(6.0-6.5'ish), then give 'em a feeding containing micros. That'd give the medium a fresh start, always a good thing.