Fishes died randomly

[PlatinumFishLover]

I introduced a healthy Arowana into it's new (already cycled) tank and it swam around rapidly and then went to the bottom of the tank and died. We introduced it to the water when it was still in the bag. RIP.
My other fish that was also in there also died the next day. RIP x2.

There are still other fish in the tank that seems totally fine and the 2 dead fish didn't look attacked at all.
What could have caused this and how do I fix it?

 

[AnthonyFish20]

I introduced a healthy Arowana into it's new (already cycled) tank and it swam around rapidly and then went to the bottom of the tank and died. We introduced it to the water when it was still in the bag. RIP.
My other fish that was also in there also died the next day. RIP x2.

There are still other fish in the tank that seems totally fine and the 2 dead fish didn't look attacked at all.
What could have caused this and how do I fix it?

Check the water andd do a 50% water change also wat size tank

 

[tlindsey]

Possibly large difference in ph and Aro went into shock. The other fish are acclimated to the ph so it wouldn't affect them.

 

[Rocksor]

What were the other fish that died, and what were the ones that are still living?