softness: me, glass, or camera?
Sorry but - it is probably you.
The first and third images in particular are ones where your D90 instruction book (the section on getting good results using AF) explains the subjects are ones where AF may not be accurate.
If you use AF on a subject where the camera is unable to AF good you can get unsharp pictures like yours.
Great images are often of good subjects.
If they are great images does what lens, body or technique was used matter more than the skill of the photographer?