how old is this tank? it maybe just a phase that your going through it would go away by itself and with the help of water changes .. it sound like you have enuf turnover rate..
Also are you using ro/di water? are your parameters good?
The hermits aren't gonna due much about the cyano, they will help, but IMO you're better off not buying them unless you just want hermits. But IMO snails would help more..