Disapearing fish and upside down fish???

Okay I seriously don`t know whats going on........
About a week ago I noticed that I can`t see all of my danio`s. But I thought they were hiding. Now some of my neon tetra`s is missing as well!!! I have angels in my tank and I know they eat tetra`s when they are bigger but these are still really small (2cm)

Another danio is swimming and when it stands still in the water it turns upside down with belly on top..... I know its probably dying but I want to know whats killing it, so I can do something about it.

Please help!

Tank info:
450Lt community tank
tetras
danios
angels
blood parrots
golden algae eaters
swords

 

How big are the parrots? They could also be having a go at the smaller fish. Keep an eye out for the algae eater as well because they are known to be boisterous.

 

Uhmm... @Soetvlei ...

Dont know the size of your Angels,but I think the suspects are your Parrots,mate... Remember that a parrot will grow to round side plate size and in its parentage used to create it,is the Red Devil,true "evil" cichlid...
There is NO LONG TERM way you will be able to keep these guys with Tetra's and danios... desiscion time mate...

Your distressed Danio has either a swim bladder problem,but I think that it got injured when the "perp" targeted it as a snack...

G'luck mate!