My kitties are both sick

They are both on antibiotics. The vet ran a bunch of tests on our older one and couldn't figure out exactly what was wrong because the tests didn't have anything stand out. Now our 3 month old is getting it. She lost her meow, is coughing and sneezing, same symptoms as the other. And she has roundworm! They're both on medicine and I just hope they get better. I hate seeing them sick