New album artwork not displaying correctly when shared library is accessed from mac mini

Here's a weird one: I recently added an album to my library on my iMac that did not have any album artwork information. I found what I thought was the correct album cover and added it to all the song files of the album. My entire music library from my iMac is shared with my mac mini in the other room. At first the album artwork showed up fine on the Mac Mini. However, I discovered it was the wrong album artwork so I updated the files on my iMac with the correct artwork, but now it is not updating on the Mac Mini. What's even weirder is that when I play songs from that album on the Mac Mini, the little thumbnail next to the playback bar at the top has the correct artwork, but the big thumbnail next to the album in the library is still the old artwork. I've tried everything I can think of to update it and it will not work!