Here's a picture of the debuff icons (up and to the left of the target frame) without the timer bars showing up.
Here's a picture of the timer bars AND the debuffs icons showing up. Debuff icons showing up in the same place as the previous picture.
Now, after some exploring, I figured out that they belonged to DUF. I disabled them so they won't show again. But I'd definitely like to know why the timer bars randomly stopped showing up (if it can be figured out that is).
Thanks for looking!