yes though it also could be dirty?Yellow water can be caused by tannins. Tannins are very healthy for bettas and contain properties that heal injuries faster. Tannins also occur in the wild and they induce spawning behaviour in Betta Splendens
you must have pretty good shops around were you are,there are quite a few shops that I'm aware of in my area, that have tannins in there tank
It's a breeder so, tannins is my guess. I'm getting pictures soon so I'll post em