Dude, not trying to be a smart arse, but you need to do some serious reading on ick and what may have caused it. If the tank was stable for 5 months, at that size, you were prolly riding on the coat tails of the previous owners efforts. I'm not saying you don't know whats going on but not treating ick is a sure death sentence as you have now learned. Again, before considering any further stock or even steps to recover, please read. Lotsa good info on google. Once your armed with good (lots) info, you'll be ready to take another much more educated swing at it.
Best of luck!
To fail to plan is to plan to fail.