Hi, welcome to the forum!
Whenever you're getting one artwork for many tracks that shouldn't have it, it typically means there's an artwork file in the folder that's taking precedence over embedded and other artwork.
Check your artwork settings in tags (1) and make sure that both storage and retrieval are set to embedded first (unless the artwork is not actually embedded, but it looks like it is). Also look for artwork files in your music folder and remove any that are called something like folder.jpg or cover.jpg. Then rescan your artwork again.