The real problem is, the mother showed no signs or effect of placenta retention or mastitis. A placenta retained 24 hrs will have the bitch feeling awful bad and not caring for pups. The mastitis being a bacterial infection would have the teat inflamed, feverish and a lump/cake could be felt as your seeing now.
I think I would have went to the vet on the 4th or fifth day, somewhere between loosing the 3rd to 6th pup. Now a week later we're sitting here talking about your bitch with
Yesterday her tits looked funny. The front two were big but the back was hard I really think it’s something to do with the milk.
The biggest threat of mastitis was always milk being produced and not utilized, as when loosing a litter or at weaning.
This may be some help as to where your at now.
Treating Canine Mastitis
Treatment depends on the severity of the condition and may include antibiotics, hot packing the affected glands, and milking out the affected glands. Puppies can continue to nurse from the affected gland if the milk remains normal. If your brood bitch shows signs of breast infection it may be canine mastitis, so get her to your vet immediately. He will prescribe some antibiotics that distribute to the milk. Mastitic milk is usually acidic, and bases distribute better into acidic milk. Ampicillin or oxacillin are good choices until a culture and sensitivity results are back You may want to keep the pups nursing the bitch if possible, because this will keep the glands drained.
Invariably the infection will cause the breast will rupture out the side, leaving a large open wound which must be cleaned daily. The antibiotics will prevent further reinfection. If there is an open abscess or gangrene, then remove pups and hand feed. Treat the abscessed gland as open wound. You'll find that when she has litters of puppies in future, she may not produce milk in the breast segment that was affected by canine mastitis.
Chronic mastitis in the bitch can occur, even if the only symptom exhibited is that the puppies are not thriving. The incidence of this condition in the dog is currently unknown. Regardless, bitches diagnosed with chronic mastitis require aggressive antibiotic therapy. Unlike acute mastitis, chronic cases may require the use of special medicines that will cross the barrier between the blood and milk.
Galactostasis
This condition occurs when milk is not removed from the mammary gland promptly. With galactostasis you see hard, caked glands because the bitch is not producing milk. Galactostasis normally occurs in bitches with small litters or when pups utilize only one or two teats. The condition can also occur as a result of a false pregnancy. As long as there is no inflammation and infection, galactostasis is not usually serious. However, a bitch with this condition is often very uncomfortable. The breeder/owner can provide symptomatic relief by soaking the glands by applying cool towel compresses. The veterinarian may prescribe diuretics or pain alleviating drugs. Reduction in food can lead to lowered milk production and aid the bitch with galactostasis. Milking the affected glands may actually lead to increased milk production. depends on the severity of the condition and may include antibiotics, hot packing the affected glands, and milking out the affected glands. Puppies can continue to nurse from the affected gland if the milk remains normal. If your brood bitch shows signs of breast infection it may be canine mastitis, so get her to your vet immediately. He will prescribe some antibiotics that distribute to the milk. Mastitic milk is usually acidic, and bases distribute better into acidic milk. Ampicillin or oxacillin are good choices until a culture and sensitivity results are back You may want to keep the pups nursing the bitch if possible, because this will keep the glands drained.
Good luck taking care of your bitch.