I don't think its too much food, but it's not a diet I would really suggest. Most of the frozen cubes are basically the same. A main filler/binder, and shrimp/krill/fish meal. What I would suggest, algae sheets should be the tangs main diet. Every day, some of the sheet. For everyone else, I would make the bulk of their diet, mysis and NLS (Spectrum) pellets. The pellets will allow you to use less vitamin supplement, as they have better retention. For the larger guys, use PE Mysis (Piscine Energetics), in combo with that Hikara mysis. Just make sure it's rinsed enough. And every other day, or every third day, use some fresh frozen stuff. Throw a scallop or two in a blender, and finely chop it up, but obviously don't pulverize it. Just a couple pulses.
The problem I have with suggesting feeding less, is that it's hard for people that might not known exactly what healthy body weights for most fish are. I've seen a lot a tangs with their ribs showing by people meaning to do well, but they just aren't feeding enough. A tank with a nuisance algae problem with fat-happy fish, is better then an algae free tank with starving fish.