I went through that when I adopted my cat Jazz as a kitten from the shelter. She also had a nasty URI but the ringworm took longer to cure. She was in isolation for about 5 weeks from the time she was diagnosed and started the meds. She also took an oral med given to me by a different vet but when my regular vet found out later he was upset. He said that medication was too dangerous to give a kitten because it could cause organ damage. I'm not sure if it's what you are using but it did start with a G and I had to have it made up special at a Medicne Shoppe. As far as we know she suffered no ill effects from it.

I think all her ringworm spots were dried up and she had no new breakouts for a few weeks before I could let her out.

Remember to clean everything well after visiting or medicating the kittens. I even used Clorox wipes to wipe down the door knobs and I kept a bottle of that disinfecting gel in the room. Also, once I let her out I cleaned the room she had been in from top to bottom, threw away the cat toys,washed the cat bed a couple of time in hot water, then kept the door shut a few weeks and cleaned it again before allowing any other pets access to it. I know that sounds over the top but I didn't want to risk going through that again. Better safe than sorry.