Why are my zebra dainios killing eachother?

I'm going to start from when I got my zebras (sry if this gets long) I dont know the dates exactly I'm just guessing around when everything happened.. In October I got 6 zebra dainios from petsmart. I got another three from petco a few days later (needed more females). One of my zebras got ich a few days after I got her so I separated her from the others and no one got ich. Like 6 days later, I'm doing a water change and after when I'm cleaning up I notice one of my females is dead. Then another died. And another. In all I lost three zebras because one of my air pumps went out. I put the female in that had ich and the remaining ones were fine. I still had 6 zebras so I didn't worry about getting more. Around a month later one of my zebras goes missing. I cant find him anywhere. My mom found him and he was beat up and dead. He was very small so I assumed he died and got eaten. A couple days later my other really small one goes missing. I couldn't find him for a day and then I found him behind a moss ball. He was obviously beat up (his fin looked ripped and he wasn't swimming right) so I floated him in a box with a plant and an air stone. He died about a day later. I got some new fish in a few weeks later so my numbers were back up to 6. Then one of my bigger ones got beat up and eaten. That was in January. Cut to now, I have all the fish I was planning for my tank (guppies, honey gouramis, and corys) in with my 6 zebras and everything is fine. Until yesterday, when I found one of my gold dainios swimming slowly in place, hiding. I looked close at him and I noticed most of his bottom find were ripped/gone. I moved him immediately to a breeding net and hes not doing so well. Hes at the top and not moving much. Hes only swimming in place. I'm not optimistic that hes going to make it. I have 4 zebras (not including injured one). They went nearly 4 months without incident and suddenly beat up another zebra. They have never seemed to bother any of my other fish. What should I do? Should I get more zebras and risk new ones getting murdered? Should I rehome them before more of my fish get killed? Should i move them to a different tank? Should i leave them as is and hope for the best? Any advice would be greatly appreciated. Thank you in advance!

 

the only reason I might think is that they are cramped. How big is the tank

 

I don't think they're exactly killing each other, it's very natural for fish to nip/pick at other fish that appear dead or dying. Sometimes said nipping ends up contributing to deaths

 

the only reason I might think is that they are cramped. How big is the tank

20 gallon long, thank you!

 

I don't think they're exactly killing each other, it's very natural for fish to nip/pick at other fish that appear dead or dying. Sometimes said nipping ends up contributing to deaths

They've ripped the two I found dead apart, and they looked like they'd been dead a week. Only they could have only been dead 12 hours at most. Maybe they were sick but my one big one was perfect until they killed and ate her . Althpugh they could have killed the small ones because they were very small. Thank you!

 

That’s typically what happens if you don’t get them immediately, once they’re dead they’re nothing more than a good source to the other fish. It can look even worse if a dying fish is drifting around as if it’s already died and the others will still nip at it

 

That’s typically what happens if you don’t get them immediately, once they’re dead they’re nothing more than a good source to the other fish. It can look even worse if a dying fish is drifting around as if it’s already died and the others will still nip at it

Ohh ok. Thanks!

 

So my injured gold dainio won't eat . He refused flakes so I'm trying blood worms or brine shrimp tonight to see if that will tempt him.

 

He didn't make it