I'm starting to feel bad about Laddie

I looked back through my journal, and his symptoms are very like what Perry's were- listless, slightly swollen appearance in the belly but very little appetite, pale color. For long periods, then having one or two good days, then just hanging at the surface again. He doesn't even notice the guppies swarming around him to grab food. He only eats if I offer garlic-soaked flake and even has trouble getting that down now. He's been doing poorly for over two months now. I just kept hoping every time I saw him suddenly acting lively and spry again, that he was finally improving, but it doesn't last. I suspect it's a virus- especially because there's viruses that gouramis get that aren't as contagious to other fish species. That would explain why the guppies and white clouds dart around looking totally normal while Laddie is so unwell.

I am starting to wonder if I ought to be kind and euthanize.