I've noticed that my betta, David Bowie, has recently become very lethargic and his coloring seems to be off. He's blue and red, but his face seems to be losing its color. It's kind of looking green/brown ish. However, near his gills, it's still very red. He is contstantly moving his fins, but he's not swimming around much. Also, I've noticed a sort of fuzzy brown looking thing growing in his tank of his plant and on the sides. I've cleaned the tank when I first saw it and now it seems to be coming back. And ideas of what this is/ how I can fix it?
Oh, also, his eating seems to be perfectly fine.
.94 gallon tank
I use TopFin Betta Water Conditioner
I've had him for about 3 months