Guinea Pig has sore-looking and red back foot pads?

Hi. I have a 1 year old female guinea pig; Hamlette. Ive had her most of her life, and I have always noticed that the long pads on her back feet (normally pink and hairless) are a little red, and look like they could be sore. It doesnt seem to hurt her, but I dont speak Pig. She lives in a 9 ft2 homemade c&c cage with a fleece bottom and paper towel underlay. I wash the fleece often. I dont know if its just the acid from her urine, as she tends to sit right on top of where she pees, but there is nothing I can do about where she wants to sit. It is not severe enough to take her to a vet, but I would if it got worse. Is there anything I can change about her cage, or any easy medications I can use? Or is it normal for her back pads to be a little red? She is very active, and loves to run and popcorn around her cage a lot, could this just be like rug-burn?