So I have this ongoing tailbiting/finrot problem. Someone suggested maybe the shells I have in the tank could be the cause, making the water too hard for the betta's liking. It's taken a while, but I finally got around to testing the hardness. My water is a bit odd, 5 kH and 17 gH, but this was the same in my betta tank just before weekly water change, so it seems the shells aren't having any effect. pH was 7.4 too 
At the moment, Lotus seems to have stopped biting/rotting and there is some regrowth.
Peacock still looks shredded, but it doesn't seem to be getting any worse. Same for the patch on his back. So not too bad atm

At the moment, Lotus seems to have stopped biting/rotting and there is some regrowth.
Peacock still looks shredded, but it doesn't seem to be getting any worse. Same for the patch on his back. So not too bad atm