Puppy with Pneumonia loss of strength in hind legs?

I recently adopted a Chihuahua/English Bull dog mix. The rescue group thinks she is about 15 weeks. They believed she had Kennel Cough that my personal vet said was actually Pneumonia. She was seen on Wednesday for the Pneumonia, given fluids and two antibiotics. That same day we noticed she seemed wobbly when she walked but thought it might just be that she was week from not eating very much. The antibiotics have helped so that she is eating a little more, and I am giving her special electrolight fluids with a medicine drop so she is staying hydrated. However her legs are getting slowly worse she now drags one, sometimes both behind her a lot of the time. She doesn't seem to be in any pain she is getting up and about just not walking properly. She goes back to the vet for her recheck day after tomorrow. Do you think her loss of strength in her hind legs is related to the Pneumonia?