Guinea pigs-bald patches

Question
Hello,
I bought two female guinea pigs from the pet store a couple of months ago after my last guinea pig died. They had both been very healthy and seemed happy. Then a month later I found out they were both pregnant due to being so large. They gave birth two months after I got them, and one had three and the other had one. The pups are now two and a half weeks old, being weaned, and are very healthy. Unfortunately in the past week I've noticed that both especially one have bald patches under their necks, armpits, and shoulders. The skin looks smooth without and blemishes, and without wounds. They are definitely doing it themselves because I seem them. It may also be the babies rubbing up against her to get milk.
Please help!

Answer
the most common cause is mange, or a similar paracite of funghi, i would recommend popping down to the local pet shop and getting some anti mnge spray, use as recomended and it should be fine.

if however you are certain that they are attacking one another then i can only suggest seperating them, and then reintoducing once they have been fully weaned fro their pups using the usual bonding methods.

best of luck