Sick angelfish, getting really frustrated now.

[Phishman1]

120 gallon tank, 13 angelfish, 3 Frontosa, all get along just fine. water parameters fine.

Suddenly and angelfish stops eating, eyes are not popping out, but it does appear a little bloated, I removed to its own tank where it died in about 3 hours.

To that point the tank was perfect all fish as soon as I walked up ate and are healthy, the remainder of the fish seem perfect until I just notice a smaller angel now doing the same thing not eating.

Foods are a variety of flakes and brine shrimp, frozen once a day.

Is that possibly a clue, the brine shrimp causing a blockage of sorts.

I'm frustrated and honestly ready to just give this hobby up after 45 years, I'm tired of putting money out to just have problems and fish dying.

Any suggestions as to what these fish have or what to do?

 

[BillD]

I very much doubt the brine shrimp are the problem. There is a viral disease that angels seem susceptible to that showed up a number of years ago, that was called (for lack of a better name) angel aids. When it first showed it wipe out massive amounts of angels including those of breeders. It normally shows as the fish not eating and hiding in a corner. It normally takes quite a while to kill the fish( sometimes weeks), so it doesn't sound like your situation.
What does " water parameters are fine" mean? What is your water change regimen? How big are the fish? All these things could be a factor.
When I have a situation where there appears there is a health issue, I do a large water change ( up to 90%). If there are water borne pathogens, the percentage of water change will reduce the pathogens by the same amount.Any reduction of pathogens or other contaminants will give the fish a better chance of fighting off the problem.