Could you provide more details, so I can attempt to recreate the issue? Some additional details which would help to better understand the issue are.
- What is the resolution of the source PSD? - What are the dimensions of the design in Adobe Express? - Does the PSD preview show the blur within Adobe Express or is it only when you save a file? - What file format are you saving to?
I attempted to recreate the issue but it seemed to be working okay for me.