Do you have any other fish with them?
I picked up this tiny, cute little one, we call her rosie and had her in a tank with just 2 good sized bushynose plecos at first and she was never shy and always friendly and hungry. After about a month we moved her to a bigger tank with some new friends, 5 corydoras and 5 tetras and a dwarf gourami that was about her same size. She immediately chased the gourami around a little bit but not bad. Then the first night the smallest tetra came up missing and I thought maybe he didn't take the transfer well or something, Then the next night 2 more tetras were dead. And I knew Rosie was a killer parrot.. lol SO I moved out the other 2 tetras, so she wouldn't get them and the next moring 2 dead Corys! So I took out the other 3 corys and gourami. I'm still in shock this tiny little Kirin parrot is such a killer. She is well fed and has plenty of room, yet killed 5 fish in 3 nights. She is still friendly and doing good.. just all by herself!