Guinea pig with dirty fur in pubic region?

Hi all!

So my female guinea pig, Betty, is 3 years old. A couple of days ago I noticed that the fur around her pubic region (extending up to belly button) was covered in pee. I assumed that she had just peed and not cleaned it yet, but I noticed this morning that it was still dirty/felt wet.

Should I be concerned? I know guinea pigs are pretty good about grooming and I've never noticed her look dirty before. I gave her a bath today and will watch to see if it happens again. I fed them squash the day before and my other sow didn't like it so I'm assuming Betty ate it all - maybe that has something to do with it?

Background: cage is clean, they're fed free choice western timothy and a scoop of pellets every morning with mixed fresh vegetables several times a week (mainly lettuce and bell pepper). No diet changes, no change in water consumption, and all poops have been normal.

Let me know what you all think!

On and here's a cute pic of them in the bath!. Betty is the one toward the bottom of the picture, my other sow Alice is the one at the top with more white.