Public Folder and reduced picture sizes

My Cloud OS 3 Personal & Network Attached Storage My Cloud Mirror
1

I have few users on my wdmc mirror and when I or other user puts pictures in to a folder that was created in public folder or even in shared pictures folder they are not the same size as they are in each user private folders. I tried move, copy , even move straight from the 3rd party hd connected to laptop. Also when either folder in public is open and I’m trying to view pictures in there I can not see the preview icons just the generic jpg file icon with file name
Can I change this somehow??