If you already put in chlorine and chloramine remover in, and his water's around 78 degrees F and it hasn't been fluctuating, then there's probably not anything you can do for him. He could have gotten sick before you got him, and his body's just giving up. Are there any bubbles on the top of his water? Has he been eating? How big is his tank?

I have had a few bettas in my time. One lived for a year and a half, one for two years, and two that both lived for less than six months. Some just live longer than others.

I'm sorry about Herman.