Fish dying/dead - Heavy Breathing - Need Help

[mws]

I didn't have to read the entire post, I know what is the problem
The only thing was changed the day prior was two new powerheads

Lost an coral beauty angel overnight and both tangs was hiding and gasping for air in a morning. All I did is added a new powerhead and I washed it under warm water. After searching the net and coming across reefers with same problem, this is got to be the coating on them.
Now I run all the pumps and powerheads in a bucket of warm water and vinegar for a few days, before they go in a tank. Keep changing the water in a bucket, the first change will have a oily film on top.

As for now do a water change in a tank, rest of my fish was back to normal with in two days.