I deselected "optimize in export" from resources button, and the results are that it is now not blurry in preview, but when exported it looks even more blurry.
The images that are coming out blurry are high res - 1000x900 PNGs and similar.
I've looked through previous threads and can't find a solution that works, please share your knowledge!! Thank you so much.
Uploaded to server here - ZIP file is too large to upload...