It sounds like the mother rabbit has rejected her babies.
Please excuse me if I'm wrong, I'm not an expert.
I don't know if this works with rabbits too, but I know that with hamsters, if you touch their babies, the hamster mummy believes her baby has been "contaminated" and actually eats her baby, thinking it will not survive because it's been touched by a human.
This might be the same way with your rabbit. Since you've tried feeding the babies, mommy might think her babies are contaminated too, and she's killing them because she doesn't think they'll survive.
You really shouldn't keep a guinea pig and a rabbit together. There are many reasons why you shouldn't allow a guinea pig and a rabbit to live together or even have their free range time together. Rabbits have very strong, powerful back legs and even a small rabbit could really hurt a guinea pig or even kill a guinea pig. You may think that your bunny likes your guinea pig and wouldn't hurt them, but rabbits only have to get excited and they can easily kick out by accident.
As far as the infection, you can clean it out with peroxide, but the wound definitely need to get it closed up. If the infection is severe, take your bunny to the vet.
Take care, I hope your bunnies do ok.
Kasey