more unexplainable deaths

Hey guys. I haven't posted on here in quite some time as my bristlenose had been breeding well.

But things have taken a turn downhill. About a month ago, some of my albino bristlenose started showing a brown mark about 3 quarters of the way back on one side of their tale. about 5 got it and it was all in about the same spot. I thought it must be ok as they all got it in the same place. After my longfin (batfink) died from what I thought was bloat, some of the albinos started to show similar bloating and died aswell. I moved all of the albinos to my hospital tank and only 1 of them has survived (the biggest male and he doesn't look good).

In my big tank I have experienced the same problem. A common female died and I caught the others eating at it, ever since then those have died aswell. Now today I saw 2 more of my commons have bloated right up and I fear for the worst for them too.
Does this sound like some kind of parasite? - as it only happens to the bristlenose that eat the bodies of the dead ones? And also how come none of my other breeds of fish or my peppermints have died? (I haven't seen any of the peppermints eating the bodies)
I know its a pretty hard answer to find but I'm honestly stumped and I don't want any more of my commons to die.

Tank is heavily planted
Ph is neutral
Temp is at 28 degrees
Nitrates has always been fine and there is another filter in there now so it should be perfect.
Food going into the tank is Cucumber, blood worms, dried shrimp, flake, and algae wafers.

If anyone has any ideas they would be greatly appreciated

-Zane

Are the bloodworms frozen or fresh? I have been told by a number of people never to use live as they can carry parasites, and also that too much frozen bloodworm is bad for them too. We've rarely fed them it for quite some time, and tend only to use it to prompt conditioning.

We had the same problem too though about 9 - 12 months ago, where they just kept dieing, no reason we could find either.

Have you tested your tap water recently? After the thaw from the last high snow fall, you can find all sorts getting into the water supply, or are there any roadworks near you that could be affecting the water?

I am pretty sure there will be lots more ideas on what it is, and hopefully maybe more informative than mine.

Angi

The bloodworms are dried out so that hopefully isn't the worry. Not to mention the clown loaches get to them before the bristlenose do.
Anyway I have just changed 50% of the water to rainwater from our water tank. Hopefully that will be a little better.
Thanks for the reply. =)