The ick is gone but every one is dying slowly, had to turn to euthanizing

I posted a while back on some help with Ick, and everyone was very helpful, again I thank everyone. It is with dismay that I report that allthough the ick is gone every one in my tank has started to perish. I took my water in to be tested yesterday because I thought that maybe my readings at home were lying because I could find nothing wrong. The LFS aslo found nothing amiss with my water. I think everyone is dying from cottenmouth disease because they seem to have the red gills and the fungus on the lips. I have started meds for this now but I think it may be to late. I am losing one fish a day. I am resorting to euthanizing the ones that are really sick so they wont suffer any more. My question is, if I lose everyone even though I have done everything I can think to do, what do I need to do to make sure my tank is good and clean so I can start over? Some one told me to wash everything in bleach water, and set up like normal, letting the tank cycle for two weeks and I should be good to go. Is this the best way to go? I dont want to deal with these horriable disease again, its to painful to watch something die that I have had since they were born.