Certain songs still grayed-out on mobile devices using iTunes Match

Hi folks!

I'm a user with iTunes Match and an extensive music library. I've been ripping a lot of old CDs to my library lately, and I'm discovering that only SOME of the tracks are appearing grayed-out on my mobile devices. (Devices are running iOS 8.4.1, Macs are running OSX 10.10.4.)

Sometimes it's a whole CD, other times it's only one track on a CD, and other times all but one or two tracks on the CD will appear grayed. Interestingly, it's always the same gray tracks across different devices. The songs in question will be gray on both my iPhone and my iPad.

Any thoughts on what the problem might be? DRM? I thought DRM didn't apply to your personal library.

Thanks!