With most diseases fish get they are always in the tank no matter what you do. As long as the fish are healthy then they will get better and either develop resistance to it or they will be strong enough to not get it. I had many obviously sick fish that I have ended up getting when I get fish from the store and tell them "give me 20 of those)and Ijust do not notice until Iget home. The fish in my tank do not get it unless they were sick to begin with. As a result Iwould suggest cleaning the tank like normal only draining normal amount of water out. Do not scrub the tank or use any chemicals or medications. Fungus only tends to grow when the fishes immune system cannot fight off the infecting organism. Angels tend to be rather sensitive to a lot of things though they are very good against others. Personally I have a 60 gallon hex with 5 angels and about 10 cardinal tetras and 4 or 5 of a larger tetra species as well as a couple tiny plecos. The tank is heavily planted. I'm personally of the opinion you have probably 5-6 too many angels in the tank assuming you were able to give them optimum conditions which has not actually happened due to the fungus. They are likely stressed. For your mixture of fish I would suggest about a 75 gallon tank and then you could probably add some smaller tetras if you wanted but keep your angel levels no higher then current.