Back issue...not sure what it is?

I started doing Bill Stars 5X5 program (into week 3), and after doing deadlifts my lower back seems to tighten up. There is no pain like I tore something, but it is sore for a few days afterwards. I tried to run, and after the first mile my back felt like it was getting tight like a knot. I can "feel" it when I get up from sitting, but it a soreness and not really any sharp pains.
 
Is the soreness normal I guess, or am I doing something wrong? I pay attention to form in my squats (never any issues after doing them), and I am pretty sure that I have the form down for the deadlifts. So any help would be appreciated.

i would have someone else watch you do the lifts because its hard to see your form otherwise, my bet is on form

yeah you shouldnt really be doing deads if you 'think' you have form down. thats a risky thang to do.

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