I am so sorry to hear you lost the little one. Maybe we can help to figure out what caused the gas, so that it will not happen to one of the others.
You are not a bad owner ... you just have allot more to learn.
All of us had to learn what is good and what is not for chinchillas.
Chinchillas are exotic animals and need special care.
There are some things beyond our control that will cause gas/bloat and then there are some that we can help prevent.
Sometimes gas/bloat can be caused by something they eat. What all did he eat in the last 3 days. Please try to list everything ... even treats.
What all is in his chinchilla pellets other than the pellets?
If you gave him any fresh vegtables or fruits, what were they, please?
But last 4 day i just feed the treat for my chin I feed them with the fresh Alfafa.Because the doctor said it's fine.After that I noticed that he barely eat everything.
When a chinchilla feels like his belly is full, he does not eat. {not eating or cutting back on the amount he normally eats is one of the first things that warns you something is wrong with him.} The belly can be full of things other than food (such as gas), so he quit eating. Another reason they may cut back on their food or stop eating is that there is a blockage in the intestines. When there is a blockage everything backs up and makes him feel full.
Also he stop moving. I think I will take him to see the doctor today but after I came back home
he was passed away already in his house. I checked his poo (we say poop - it sounds better ) but I can't find them.
That sounds like a blockage. If you watch their poop, it will tell you allot.
(1) Normal poop is oval, moist, but firm.
(2) Dirrhea poop is more round, wet and mushy ... you often find it stuck to the shelves, the fur and the leaping ledges. Dirrhea is not good.
(3) Dry poop is much smaller, dry and hard ... you usually see this when a chinchilla is dehydrated. A dehydrated chinchilla is not good. You can usually see/feel the spine sticking out under the skin, also when a chin is becoming dehydrated.
(4) Poop covered in what looks like raw eggwhite .... this is very bad ... it is often signs of infection or parasites ... these can chill a chinchilla quickly.
The hay and pellet is the same level He didn't eat and drink at all. His Belly was really big i think it's full with gas.
Anytime a chinchilla cuts back on the amount of food or water he eats/drinks, even if it is only by 25%, this is a sign something is very wrong ... if the chin is in his regular home and there has not been anything to upset him.
In the wild, chinchillas have to hide the fact they are sick or injured ... if they don't , they can become easy prey for other animals. They still carry this trait today. You have to watch them very closely every day to learn what is "normal" for each one, this way you may be able to see the early signs of illness.
Please let us know what the doctor says was wrong with your little one.
In the meantime, clean the cage real good and make sure there is nothing in it that could harm the other chins.
Jo Ann