Injury Scabs on the upper lips?

This can sometimes happen if a guinea pig eats too much acidic fruit like oranges. Fruit should be kept to a twice weekly treat.
Do you know if your pigs get on very well? One could have bit or scratched your guinea pig there if they were a little annoyed, even if they were not fighting properly.

It can also be cheilitis or a bacterial/fungal infection -- see https://www.guinealynx.info/cheilitis.html. The picture there is a pretty bad case -- it doesn't usually start out like that.

I see.
Too much fruit - yes. I knew that but they were so happy to get fruit. But they are getting a bit bored of it now so I'll cut down. Cucumber doesn't count as fruits for this does it? I finally made a correx cage - 3' x 4.5'. It's the world's worst correx cage but they seem happy with the extra space anyway. It even looks big enough for a third. The thing is, they stopped drinking water since the new cage so cucumber is the only way to make sure they are not thirsty.
I will keep an eye on any possibility of anything fungal but for that time it looked very much like scabs from a regular bleed.
They were getting a bit playful with each other lately. This piggie with the scabs, Chubby, has been getting some goop under her eyes every now and then over the months, and I took them to the vet but the vet said there's no goop now so it's fine. Somehow, recently she seemed to have taught the other guinea pig to lick her eye and that seemed to have sorted it out. It's all very weird to me but everything looks fine, except they still lick each other's face even when there's no goop. And sometimes they don't want it when the other does it. But that leads to scabs on the upper lips? I'm not so sure.

I know if they fight they use their face/head/mouth/teeth, but can that lead to the bleeding lips? Yeah maybe.

Well 2 smaller scabs there the next morning and when they fall off the area looks very much like those fungal infection pictures so spot on. The vet it is.

Cut down the fruit and see what happens, hopefully this will sort out the issue. If your guinea pig bites the other pig's lip in the fight then yes, the lips can bleed and scab. However if you don't see them fight the chances are that they do not. If they did before then the bigger cage has hopefully made a difference.
Cucumber (or bell pepper if you were wondering) does not count as fruit. There is a list of good veggies for piggies and when to feed them on this forum, I recommend taking a look.