bitting

I have 2 guinea pigs (females) . One is 2 years old and the other is 1 years old. They have a big cage and are taken care of regularly . They have lived together for 4-6 months and there was no fighting. But one day when i was sleeping i heard really loud noises of them fighting, so i separated...

My guiena pig ive had for 3-4 years and they are the sweetest. they cuddle with me and dont bite. about a week ago my guiena pig was diagonosed with a IRT, so we have to give her medicine. ever since she got an IRT, she has been biting on me very hard. Can anyone help? i dont want to hurt her...