Corys Bleeding!?!

[Gemini]

I've never seen anyone chase any of them. The shark will sit next to them eating and they won't move - the shark goes near the BN and he flys off. That cory is healed now fine - one of the others has a small line. It seems like a wound as opposed to a bruise if that makes any sense... But doesn't seem to hinder them or affect their behaviour. It's random!

[Northernguy]

I have lost pepper corys the same way.
I switched over to sand and I lost two more the same way after a few months.I don't think its a cut but it appears to be under the skin.
What causes septicemia?

[Gemini]

Hmm from what I've been reading its caused by injury, poor water conditions, stress, infected fish food etc. I know it's not poor water - why breed in poor water? And I check it and it's always 0/0/<10
Stress - well I would have thought they would change behaviour or hide. Not hang out normally and be their normal cory selves.
Injury - well how? And why is it hitting them one at a time and healing within 36 hours??
Fish food - well I only feed them Hikari and Omega One. I would sure as *** hope its not the food. I haven't fed them bloodworms or anything in a couple of weeks. And when I did they were Hikari bloodworms.
They are still all kicking. None of them die at all - none of them even act differetnly.
Its like a scratch on our arm. We notice it but doesn't affect us at all and it goes fast.
Gee its confusing!

[Northernguy]

I havent any idea what it is.It is strange.
I have lost 3 in the last 4 months like that and all my other fish were not effected that I could see!