fish not eating NEED HELP

What are the dimensions of your tank? What fish do you have in there? What is the pH, Ammonia, Nitrites and Nitrates? What do you feed? Did the fish show any symptoms before they died (for example, stopped eating, thready white pooh, swollen body)?

the water is good i test it all the time he looked like his belly was fat its mostly male peacocks 2 small tawain reefs and a nother hap ivory top im not sure what the real name is most fish are 3 to 5 he was 2.5 or so i feed newlife spectrum a lil brine shrimp flake and sprilua flakes

If the belly was bulging fat it could have been bloat. Usually too much brine shrimp or the like for a fish with mostly vegetarian habits can be the cause.
Basically the fish's intestinal track get clocked up with meat. Death by Big Mac.

there are some white stringy stuff

Could you answer the remainder of the questions that have been asked in the posts above so that we can try to help you?

We don't have enough information to give advise without the answers.

Kim

nitrate 0, nitrite 0, total hardness 150, total alkalinity 200, ph 8.0, amonia 0 they rub alil but not alot iv lost half now there color is faded,some dont act like anything is wrong and are just fine seems my bigger fish got sick and died i did see a large white spot on ones side that died but thats the only one that showed anything there bellys are really fat on a few and theres 3 that dont eat seems like they stop eating and die 4 to 6 days later i dont see any thing in there to tell me what it is so i treated for fungus and bactiral infections the ones who were acting sick are no better its been 4 days so im lost im thinking of killing them all and starsting over not sure what to do???

What did you use to treat the tank?

How long did you treat them?

It sounds like you might be dealing with a bacterial infection, possibly Columnaris. It is deadly, and spreads quickly through the tank.

I would lower the tank temp to 76 slowly to reduce the spread of the disease, and treat the tank with Maracyn and Maracyn II for a minimum of 7 days, preferably 10.

I would also get a second opinion on your water parameters. Unless this is a heavily planted tank, zero nitrates are impossible.

You may have more than one problem in the tank, but a bacterial infection would be the one I'd want to get a grip on first.