Hello there. First of all welcome to the forum. Next, how did you get this tiny baby? Do you have her mama? If not, she is way too young to be taken away.
With this age, you have to feed this puppy every few hours. Blood sugar issues are really hard to catch sometimes.
I would wait until she grew up a little bit. Keep feeding the soft food every couple of hours, and if she has these 'seizures' give her a little bit of honey, karo syrup or other sugar.
I had a young dog that actually put me in bankrupsy! I had all those tests done, and the neurologist told me she had idiopathic (unknown) epilepsy. She has been on phenobarbital since.
As long as the ultrasound is OK, I'd wait. I assume they ruled out hydrocephalus? That is water on the brain. She would have a really large head plus other symptoms. Good luck.