FishDude...that's a good menu, but coral protein lacking. They may have been healthy with good color for a while but lacking nonetheless and eventually they die prematurely. This is typical of angels in captivity. These animals can live for over 10 years and possibly twice as long. Three angels in 15 years may be good on the trade standard, (I'm sure most die within the first year of being put into a tank) but as of meeting their potential longevity, it's no where close. With a sponge fortified food included in that menu, they may have lived a lot longer. Please don't be offended. It sounds as though you've done well considering the majority of these angels don't survive even one or two years in captivity.
It's easy to spend 20 bucks a month on frozen foods for their angel...even ones with sponge in it and still doesn't compare to when they are given free access to graze on coral, but sponge fortified foods will up their chances of a longer life in captivity. It can be just as easy for someone to buy a piece of coral like polyps once or twice a month or so. I know someone who has a 300 gallon tank with seven different species of large marine angels. It's largely an SPS tank and these fish have been in there for nearly 7 years now...peacefully together without any signs of old age or disease. They don't seem to damage much of the coral. What they eat grows back. Stuff like feather dusters and clams don't stand a chance, but they do graze on some of the coral like polyps, mushrooms and natural growth sponges, sometimes even on a SPS. They are the healthiest marine angels I've personally have ever seen in captivity and that's because of the free access to coral protein. SeaWorld's marine angels don't look that good!! LOL.