Link to the website does not work.
Re your question, if you get the same issue across different lenses and different cameras I guess I would look at what is always the same. You say you always use a tripod, so what about SR? Do you have it on or off? It should be off when using a tripod and I can say from personal experience that leaving it on can cause soft images.
Beyond that thought I would look at the processing workflow, RAW files (assuming you shoot RAW) need work to be sharp. Out of camera they can be soft.
---------- Post added 12-11-15 at 02:22 PM ----------
Originally posted by Mattox Thanks for the feedback. I was kind of hoping that the camera and lens would do all the work itself.
I consider the camera / lens to be about 25% of the image. Part is the creativity of the photographer, correct light and so on. The balance is in post processing.