Support Tiny Thumbelina's Health Journey

Thumbelina is a sweet and super tiny 8 month old kitty. I recently took her to the vet because she had had a chronic runny nose that hasn't went away. I found her under my car back in October, I took her to the vet and she was given antibiotics. After a few weeks her runny nose went away, then all the sudden it came back. She had some testing done a few days ago and she is negative for any respiratory infections, leukemia and thyroid issues. Everything came back normal so the next step is sedation so they can see if she has any polyps or what could be causing her low weight and slow growth and also her chronic runny nose. She is the size and weight of a 3 month old kitten at 8 months old ! Any help would be appreciated. Thank you