you've got to find a "happy" median to shoot at. shooting at that high of an ISO is killing your pictures, it works for the last one and i love the last one but the rest its an eye sore, your photographs are good but the quality is just the problem.
try shooting at a lower aperture, you are close enough that you dont have to worry about having too small of a DOF.
Another thing that distracts me is in your first one, the motion of the drumstick, really takes away the emotion, i see a lot of emotion in his face as he plays and itd be a great shot if you had froze the drum stick either hitting the symbol or coming right back off of it.
Give flash a try, use it very subtly and you can work wonders.
a little more light on the second one near the neck of the guitar would of added to the picture but also would of made the grain more apparent i think.
i hope you take this all as just trying to help out.