38-380? Super Zooms are just not very sharp. They are not that sharp with the lens retracted and the more extended it gets, the worse it gets. The problem is that they have to be so very finely tuned that even a few weeks of wear from heavy use can throw them out of adjustment. The rule of thumb for zooms is that the ones with the smallest range of focal lengths are the sharpest. The sharpest lenses of all are primes, that don't zoom at all. Lenses that zoom a lot have the most problems.
That said, 1. did you clean the back element of the lens? 2. What did you use to clean it?
To clean the rear element, you have to remove the lens and clean the glass on the back end of the lens. That is far more critical than cleaning the front. Set the lens pen aside and do this: [link] That's how professional restorers do it.