You should have bought a fish eye adapter with a 52mm thread to go straight to you 18-55mm lens. No adapter should have been required. Any filter or adapter you buy for your lens should be 52mm. Avoid conversion adapters. Go straight to the right size. There is always a right size. Just keep looking.

I'm not sure about the blur. Semi-fish eye adapters have very poor optics. Pictures shot with them can be likened to those taking up Lomography.

Once I had this same problem with my semi-fish eye adapter. I didn't notice any problem with the lens whatsoever. What could go wrong with a lens that has no moving parts? Before throwing it away, I decide to get a clean lens paper and wiped the glass. Both ends. I began to test it one final time and to my surprise, it was clear again!

If this does not work with you, the problem may be with the adapter pushing the fish eye further away from the main lens. If you still can, you should consider returning the items.