From what I gather, ick cures don't actually kill the ick on the fish but destroy the next larval stage to break the cycle. So maybe this takes more than 5 days. Eventually when the ick on the fish dies (not sure how long) their larval won't take over and the epidemic stops. I'd continue the treatment though for a few days to be sure. If it doesn't work, maybe you'll have to put the fish into a hospital tank without the scaless fish, so you can hit them with a full dose.