Trying to find out what killed my fish.

[Cichlid-dude]

About a month ago i had something wipe out my tank of african cichlids. I hadn’t realised but my heater failed and the water got pretty cold and they developed some white spots that looked like sores and it also looked like they were bleeding.

Whatever it was killed them very quickly, less than 24 hours and all my fish minus a pleco died. The pleco was unscathed. I just want to figure out what this stuff was. Ive attached a pic, any help would be awesome, thanks in advance.

 

[Fishlegend]

Oh NO !

That looks terrible! I don't know what it is but the fish got it from vein stressed with cold water! Which left it's body unable to defend and it immune system failed.