Lisp b/c space between top Essix retainer and roof of mouth?

[maggie20mt]

Hello, I just go my braces off 5 days ago. I am slightly not completely satisfied with the results. My clear essix retainer on top gives me an "s" lisp when I speak that is extremely noticeable and bothers me. I think it is because of the space between the part of my top essix retainer following the roof of my mouth. I does not touch the roof, but merely follows the shape of it just underneath. Is this normal?