The above site will help become informed on ich and how to deal with it. I am going to focus on what I can see to be stress factors that can lower a fish's immunity and make them more suceptible to ich and other ailments.
The 65 gallon tank is way too small for the population and some of the species you have. Triggers are large and highly aggressive predators and demand their space. Depending on the species of wrasse and their adult size, also need lots of open swimming space. Puffers also, depending on species, get fairly large.
"Really low ammonia" can be too much and start poisoning the fish especially if the pH doesn't go down. The ammonia needs to be under control and stable at zero.
Once you have the info you need and treatments are done, I'd suggest you think about what you can keep in the tank that won't outgrow it or cause stress among the other inhabitants of the tank.
Keep on changing water...about 10% once a week should be fine. If ammonia levels continue to show, then do the changes twice a week. If nittrite and nitrates are zero, you shouldn't need to do this for too long. Cut back on feeds a little until everything is under control.
How long has the tank been running with fish in it?
How much and how often do you feed?
What type of filter do you have?
How often and how much water do you normally change?
Can you list the fish in order of introduction, please?
What is the SG
What temp is the tank set at?
We, as a people, know so much more about outer space than we do about our own oceans. This lack of knowledge can very well spell the dangers that lay in wait for us.
The oceans surely would swallow us before a rock comes down to smite the planet of it's life.