So after 8 weeks my cycle was almost done. Only only that was off was nirite which was at 0.25.(coming down from its nitrite spike) I went ahead and added the 1 Oscar and 4 silver dollars. So this is where the fun starts.

Day 1: 2 Silver dollars die presumably due to stress. So I return them and get new ones. They do fine over night.
However nothing in the tank will eat. The Oscar found a spot behind the plants he hides. The silver dollars are hiding however they do come out. They dont eat either. I have lettuce in the tank from a vegi holder which they dont touch. The Oscar comes out when Im not in the room and he will pick at the lettuce. I put pellets in there and he will eat one a day. Most of the food is on the bottom. (Its not a lot)

Day 2: Oscar is still scared of me which I assume is normal however the silver dollars are my main concern they still arnt eating. I just heard an aweful noise from my HOB filter I figured some air got in it but that was not the cause one of my silver dollars got sucked up. This fish was not dead and the suction on this is not a lot. Im guessing they are weak or sick.

Next problem I just did a test on my water and things are all out of whack. The Ammonia is low and sitting at 0.25 The Nitrite is at 3 and the Nitrate is at 80.
Even if the tank was not done cycling all the way it should not have gotten out of hand this quickly. Im doing 50% WC daily and hope it will catch up. What can I do about these fish not eating. The Oscar is being feed small pellets and the silver dollars have that lettuce and some vegi flakes.

How did you cycle the tank? Also, how big were the fish that you put in there, i.e. the Oscars and silver dollars

Fishless with pure ammonia
Small. The Oscar is about 2 inches and the silver dollars.. are about an inch give or take.

How long did the cycle take you, and how high that the ammonia reach

8 weeks total
First half the Ammonia was kept at 5ppm until the nitrite came along then it was kept at 2ppm.

I am surprised that it took that long. Because it is a fishless cycle you should be able to add more ammonia which in turn speeds up the cycle. The fact that you have a fairly high nitrate does indicate that your biological filter is working. Nitrites of three is very high and certainly life-threatening towards your fish, you might be advised to get some prime which will detoxify nitrite and ammonia. I would advise you to limit the amount of food going into the tank at the moment, only once a day, and not too much. I assume that you're not turning your filters off at all?

These sort of things can happen when you first start of the tank. You have introduced fish for the first time and started feeding them, and that in turn is going to create ammonia. A newly established biological filter is quite delicate and you can run into problems if suddenly a lot of ammonia is being introduced at once. Carry on with the water changes and hopefully things will settle down within a few days. Don't touch your filter at all, don't turn it off and don't wash any of the media for the time being

I dont turn them off right now I have the HOB out of the tank to get the silver dollar out. Will the fish be okay with just 3 of them instead of 4? The Oscar is coming up when I hide behind my computer monitor and will eat 2 or 3 pellets. But the silver dollars still dont eat. Any ideas on that? Ill grab some prime and continue to do the large WC every couple of days until this is under control.

Sorry, I was in the chat room, you should come in sometime

at the end of the day I am just surmising at what the problem could be going by what you are telling me. Nitrite of three is very high and that could be the reason why some of your fish are reluctant to eat. It could be that they are very shy so just give them time. However, until you get your water commission sorted out, you won't know if your fish are behaving this way because of it. Are the Oscars breathing heavily at all?

Like I said in my previous post, please try and avoid feeding too much because that just increases the amount of waste that goes into the water, i.e. ammonia. Even though your filter seems to be dealing with the ammonia okay, it is struggling with the nitrite, or so it seems.

You haven't said how big your tank is?

Oscar is not breathing abnormal. Its a 75 gallon tank. I am going to get some prime. Also some shrimp to clean some of the food off the bottom. The substrate is thin and trying to suck it with a gravel vac would suck the sand right with it.

Don't get any other living creatures, even shrimp will add to your bio load. General elbow grease is the only way to keep your tank properly clean, don't rely on fish, they will only add extra waste so will actually defeat the object

I feel your pain and am sorry you're having trouble. I killed 3 of my 4 Silver Dollars (after 10 years!) almost instantly - well, within several hours of each other - all because of the water chemistry and a newly cycled filter.

There will be light at the end of the tunnel - don't give up. Once established, the SD's were very hardy and easy to care for fish - at least they were for me - 10 years of no issues. All of this hassle will be worth it in the end.

Are your fish gasping? Do you have plenty of aeration in the tank (lots of bubbles breaking the surface of the water)? That is the only thing useful I can think of to add that hasn't already been covered.

How is the tank lighted? Are the lights very bright?