do as many water changes as the meds will allow. This is because ich will free float in the water looking for new hosts, by doing water changes you can remove a substantial amount of floaters.
And this isn't your first go-around with ich either.... I'd look at a quarantine tank in your future. Put any new arrivals in that tank to be monitored for around 2-3 weeks to make sure they are free of disease. A little preventive measures can prevent all this hassle. I didn't believe in it until I got a severe case of columnaris. Now it's common practice. Besides, one day when you get guys like this, you want to keep your tank as clean as possible:
A quarantine tank can just be a simple: filter, heater, and some PVC
/fake plants for hiding places. It's temporary so nothing special.