Sorry to hear about your disappointing results. It sucks when patience and diligence don't pay off. I've never done an 8 wk qt and even though some of my fish have had ich, I honestly believe that it was more brought out by stress factors.. I know that's a toxic satement in some of these forums but IME I have done more damage panicking at ich then saying relaxed and letting go. I have done freshwater dips and various additives. Nothing eliminates it IMO.. My recent example was about 6 months ago, I had a kole tang that was eating and doing well. I then added a blue hippo and within 3 days they both had it. The blue hippo, being more aggressive and voracious eater must have intimidated the kole because it stopped eating. Within about 3 weeks, I lost the kole tang. However, the hippo has been perfect since. Not even the slightest white spot on him.. I think that the stress of being transported to a new environment and effort of establishing the pecking order brought it on. I may be very wrong, but these are my observations. All in all, I think as long as they are eating well, leave them alone.
This hobby does have it's share of F you moments but hang in there. The more difficult the puzzle, the greater the feeling when successful. Good luck and I hope all your fish pull through