Feed them Mezuri 6F rodent breeder diet.
What you are feeding them does give them food, but not what they need for breeding.
Breeding an animal takes a huge toll on their bodies and you have to give them the best food you can.
Would you make a pregnant woman live off peanut butter and crackers, raman, and potato chips? No probably not, you would give her the best food you can to make her strong and make the baby strong.
Start with strong food and you should have strong breeders.
If you were not breeding them I would say what you are feeding would work,still not the best, but you are breeding them so they have to have nutrition and energy.
I hope this helps some, if you have any more questions feel free to PM me I will get back faster.
Mike