We need more info. What is done in Photoshop before saving, exporting? Can you post screenshot with Layers panel visible. What is version of Photoshop, which OS you are using?
We need to know your operating system and version?
Photoshop version?
A full res screen shot of the image.
Have you tried saving the image and opening it in another app? That would tell you if it's a display issue in Photoshop, or the issue is baked into thew image.
Any other information you can think of, and the more the better.