How can I help my kittens get over their colds?

I just adopted 2 kittens, both 2 months old. At first, my little girl (Juno) was extremely healthy and my smaller boy (Boba Fett) was sneezing and icky looking. Eventually, they both got sick and the vet gave me antibiotics. I’m not sure what they have, but they both sneeze, have runny noses (which are now VERY stuffy) and Juno has become extremely lethargic. They’re both eating and drinking but Juno can no longer breathe out of her nose. Boba is doing much better, Juno is getting worse. What can I do to make it easier for them both? I don’t have a humidifier or anything like that…is there anything I can do from home? I’m only on day 3 out of 10 of giving them their meds.