All I can really say is that you need to get him to the vet as there isn't supposed to be a reaction like this to wormer. I think you might have gave the wormer to them too soon without knowing that they had them for sure or not. Some people actually throw them out because they just don't want them, and they are perfectly healthy. Hope you take him in to be seen, good luck to you.
Your puppy could be having an allergic reaction to the wormer or perhaps was given too much for the pups weight/size. The jerking sounds like it could be having a neurological reaction. The pale tongue could be anything from lack of iron, dehydration, kidney function. I would take the puppy to the vet to get a professional diagnosis and treatment right away!
Your puppy needs to see a veterinarian immediately. This could be related to an overdose of dewormer depending upon what type was used or there could be a different cause for the illness. In unvaccinated stray puppies distemper and parvovirus are always a concern. Twitching or neurologic signs are not normal and causes can be serious. Pale gums means lack of tissue oxygenation--could be due to anemia (low red blood cell count), bleeding, or low blood pressure. These things can be life threatening as well. Puppies do not have a lot of reserve. Their immune system is not fully developed. They are sensitive to dehydration, hypoglycemia, and hypothermia. These dogs need care from a veterinarian to treat this illness and preventative medicine for healthy development.
