You need to remove those fish to a qt. You need to leave the main tank fallow (without fish) for 6 to 8 weeks to allow the ich to die off, if you try to put the fish back before that time more then likely they will get reinfected and you'll have to start over again. Do not treat the main tank. In the qt you can either do copper or hypo if you don't have alot of experience I wouldn't do hypo. If you go copper try cupramine by seachem it works great and is a form of copper that is not so stressful on the fish. Make sure you follow the directions and you'll need a copper test kit I would use the one by seachem also. Make sure you watch the ammonia levels. Good luck.