It sounds like the pups were 26 days old when the mother died. So almost four weeks. The pups should have been at least 4 or 5 pounds by that point. IF they are all GSD.
Then the breeder has been managing them for another week after the mother died, and doing somethings wrong. The adult food doesn't bother me, but the milk does. Cows milk is notorious for causing loose stools in dogs. And, loose stools mean the pups are not getting the nutrition they need. So they can be losing weight for that alone.
Add in the ticks, and the pesticide, do we have any idea whether they have been wormed?
I think the puppies need to be evaluated by a vet, and then fed many meals per day of appropriate dog food. Since they are so small, I would probably use a bitch's milk replacer rather than warm water, and a higher quality kibble. And I would feed them 4-6 times a day until they are gaining properly.
If there is a worm load, you might have to deal with that before you can get the weight gain, but the dog will need to be stable enough to handle the worm medicine -- so you need to be working with your vet to try and plan what is best for the pups. I probably would not vaccinate these pups the way they are, but I would not take them anywhere either, until they were vaccinated. I think you need to get them worm-free, parasite free, and solidly gaining weight before doing any vaccs.
A bitch with pups should never be left with a collar on. So many things wrong. These people sound really awful.
Heidi Ho, Odie
Joy-Joy, Bear Cub, Hepsi-Pepsi
Cujo2, Karma Chameleon
Ramona the Pest, Kojak -- who loves you baby?
Tiny Tinnie, Susie's Uzzi, Kaiah -- The Baby Monster.