I have had this Betta in a 4 1/2 gal freshwater tank, live planted, canister filter and heater, and have timers on the lights. I've had him for about a year at my office. He started changing color on his back - just a place on his back that turned white. Its spreading and is now on his sides. Looking up close his fins look perfectly normal to except they are changing color. His appetite isn't as good as it once was but he still eats. I've been using Melafix and Pimafix but neither has helped. I have nerite snails for algae control so can't use anything copper-based. Any idea what's wrong with Blue and how I should treat him?