4 week old pup with neurological problems.?

Last week I brought my pup from my litter (mom takes very good care of all 3 pups Problem one included) to the vet because it could not even sit up while the 2 others were walking around and my last litter of 7 were also walking at this age The vet said that the signs show some kind of neurological problems( slower growth with bad balance) She said that the pup could develope but at a slower rate and we talked about leg exercises. Witch I have done and am firm beleiver that is why I have had progress. Vet will be incontact with me in a nother week. And I do plan to keep her. I would like to know if any one knows of other things i can try sorry last question so vag I'm new at this