Ich naturally falls off of fish and its common for people to think that whatever med they stuck in their tank worked.
There is no "reef safe" medication that works on any consistent basis with ich.
If you want to cure ich .. then catch the fish .. QT them and treat with either hyposalinity or copper .. leave the show tank without fish for about 5 weeks (ich will die off because they require a fish to perpetuate their life cycle).
Here a nice short article which may help.
http://www.petsforum.com/personal/tr...marineich.html