Betta Tumor?

[Sien]

Hi. My betta is getting pretty old, I got him late 2017. I was wondering if anyone knows what this is? It is possibly a tumor? Unfortunately my betta has been in slow decline. Seems like old age and this thing on his tail is getting bigger, starting to weigh him down.

 

[BigManAquatics]

Tumor or possibly fungus, can't really tell even when i zoom in. My eyes aren't always so good!

Not fun watching them get old.