Wile Dwig's suggestions are very sound there is two things lacking. These could account for the unsharpness, I can see a disteinct lack of stability in your setup. Your rig is very front heavy, even when pointed down the way you have it there will be some vibration. You would benifit considerably by finding a means of centering the weight of the camera, lens and extention tube. One way I can think of to do this would be to find tripod ring that would fit your extention tube. Granted these are ment for telephoto lenses but the same principal would apply, that being centerweight balance.
I do mine considerably differently, I use a bellows enabiling me to move the entire rig with ease. It uses a focusing rail that I can either centerweight on the tripod
or I can use the pin in the focusing rail to stabilize the unit. (not the greatest snap of it but...)
What I'm getting at is stability, Stability is key in macro work, it's more important in macro than it is in telephoto photography.
One way you can reduce vibration is use the mirror lock and shutter release delay, I use both regardless of how stable I have my rig set up.
The second thing Dwig did not mention is the use of AF, Now given that you appere to be using a reverse lens setup so this does not apply to the current set of photos. But, for future reference, always use manual focusing when doing macro work even with dedicated macro primes and/or macro filters. The shallow DoF will nine times out of ten confuse the AF resulting in missfocus.
