Update for today.
Another fish seems to have finrot on it's caudal fin. Now I'm not sure if this will be culmnaris or finrot. There are no cotton wool like marks, or fungus, just pieces of the fin missing, the fish seems to be fine, swimming about eating etc. I've just bought a 6.5g clearseal tank for a quarantine tank as this looks different to culmnaris that I already have, and I was going to treat this with Interpet No 8, but before I do I would like to see what others thought. Keep it in the main tank and treat as culmnaris, or quarantine, and treat as finrot. I've looked at loads of pictures and read a bit more about it, and can't see any resemblance to culmnaris with this one.
So at the moment, BGK died, 1 angel treated successfully, 2 fish with culmnaris, and 1 unknown.
This is turning out to be a nightmare, when I think I'm over the worst, BAM, there's another problem to deal with!!!