Using wide angle lens adaptors
The quality of the image is milky when I use the wide lens adaptor and zoom right inIt's a lens adaptor or a supplementary lens and designed to supplement the existing optical range of the built in zoom. To widen the field of view at the wide end and the tele end of the zoom. It's a big ask for a zoom lens to perform brilliantly at the very end of the telephoto-end of the zoom at any time.
Adding a piece of glass designed to widen the shot makes this task even harder as you extend the zoom to try an magnify the image as much as you are able. Without the wide angle adaptor on the front, you would find yourself not having to stretch the zoom so far, taking it well out of it's comfort zone. This is why you had a disappointing result.
Do all wide angle lenses have a soft edge when we zoom in or is it because I have a cheap lenses
Many are soft at the edges, even expensive ones. The cheaper the lens, the worse it gets. I use the wide angle adaptor only when i need it for a wider angle of view. I take it off if there as just run of the mill shots to capture.