Seven nation army tabs - what am I doing wrong?

3-5-5 and 5-7-7 are a full step apart. i honestly don't understand why they would sound the same. however, are you using an octave pedal? are your string relatively new? are you in standard tuning? what the guy from ultimate guitar.com is playing is correct. what he shows you when you change the tuning should be played with a slide. takes a bit more practice to get that one right.