Dang, sorry you lost all your fish! That's the pits. I noticed that you had a lot of fish for this size tank. Diseases like ich really don't bother healthy/unstressed fish IME. This time around I'd suggest slowing down the fish introductions and keep the total amount of fish to maybe 3. Although your scape looks nice I would suggest more rock to make the fish feel safer as well. Or you can strategically chose fish based upon the area of the tabk they hang out. One fish that wants to hide in the rocks, one fish that swims in the open, and one fish that lives on the sand for example. This way each fish has its own special zone without competition. Remember that ich and other diseases can come into your tank just as easily from CUC and frag introductions so it's almost always easier to build a ich resistant tank vs a ich free tank.
I know you didn't ask but sometimes this old salt (20 yes in the hobby) can't help himself lol!
By the way I love gold assesor as well. Mine is a beautiful and active fish, always out! But he is impossible to get a good picture of lol!