It didn't just "happen", I just happened to notice it while doing a test of all of my favorites.
I figured I just ripped crappy versions from YouTube. So I got a new one as a test that was definitely black on YouTube, "Star Wars" and replaced it.
mGalaxy still shows it as grey. So I looked at Stargate. The space field is jet black in the MP4 video, but when it runs within mGalaxy? The blacks turn very grey.
I'm surprised it wasn't my original video being at fault. I have to say I'm happy I don't have to redownload like 30 odd new videos snaps.
However, it would be nice if the grey thing stopped happening. lol