Of the 3 remaining cories:
* 36hrs later and Strange Anal Finned Cory has had the whitish swelling lump (identical to in the earlier videos) fall off again, so the two 'stumps' of where his anal fins should be are almost normal again albeit reddish. He's in great form, though - very lively and active and foraging ferociously.
* Bent Spine Cory who had become normal for a few months developed another 'mark' in his caudal peduncle near the caudal fin a few days ago, whether by coincidence or because of a collision with a tetra when going up to get air and the tetra was going up for food; this 'mark' has happened repeatedly over time, as though it's an injury, but usually resolves itself; on this occasion, though, it's looking identical to Strange Anal Finned Cory's whitish, pus-like swelling surrounded by a slight fungus-type 'cloud' and red streak. He's also in great form, though - very lively and active and foraging ferociously.
* Asymptomatic/Healthy Cory has been hiding for 2-3 days. I've shone a torch in and located him, and he is alive, responds to the torchlight and starts foraging, but is hiding behind the rock-like cave.
Do I:
* leave them be and hope that Bent Spine Cory's 'swelling' resolves itself in the way that Strange Anal Finned Cory's 'swelling' has broken off/subsided and that Asymptomatic/Healthy/Hiding Cory comes out of hiding?
* move all 3 cories into the QT to keep a more watchful eye on them and prevent any 'contamination' to the x-ray tetras and harlequin rasboras?
* move all 3 cories into the QT and dose with eSHa 2000?
Looking at them physically, my inclination would be to use the QT and dose with eSHa 2000, in the hope that this might help combat what seems to be some form of (recurrent) finrot in 2 of them. Looking at the behaviour of the two who have outward physical signs of problems, my inclination would be to leave them where they are as they seem perfectly happy and I wouldn't want to cause undue stress.
Whatever happens, I will NOT be replacing them - it's as though someone
is trying to tell me "Thou shalt / can not keep pygmy cories".