Do you have enough hermits to eat all those fish once they die? 8O
It might be hard getting them out of that coral-packed box you have there. The corals look great- they can actually stay happy packed in that way. At least, they could until you packed it in with poop machines that will beat their fins on them and rub their noses raw on the glass swimming backandforthandbackandforth.
I won't be judgemental- I overdo everything I have ever done. However, your fish will NEVER be happy. Which won't matter for too long, because unless you get rid of some, they will get rid of themselves.
Your tank is too small to have the tang only, and no other fish. Your tank is too small to keep a mandarin fed. What you have is a basically a Nano tank. You could get by with a small pair of Oscillaris clowns and the blenny. That would have it pretty full IMHO. The cardinals are open-water fish and will not be happy. The damsels are evil and will ruin your life. They will drink all your beer, pick at your other fish and corals, and sleep with your girlfriend.
You really HAD a good thing going. Maybe it's not too late to get it back.