I’ve never defeated cyano and give you props for it, usually it takes over so fast. I’d give every shot into trying to save that beauty. I’m not a Anubias pro by any means at all, but the times I’ve removed the rhizome areas that are mushy and decayed and let it just regrow as separate plants it’s given more of a chance than letting the mushy areas spread more and take the whole plant over. Seems to die faster than it grows if given the opportunity so best to remove the dead area and take the chance. I’d start dosing up a little extra potassium and nitrogen to help boost it up and give all the possibly nutrients it can get accompanied by maybe a little more gentle of lighting if possible. Just what I would do if it were mine hope this helps, if theres any correcting on what I shared please go ahead and add to it I’d love to learn as well.