Why is water in toilet tank brown and even though I turned water off, it's still like hissing(for lack of a better word)?

Good morning,

https://www.kapwing.com/videos/678298ef964f22b2dad5f977

Hope you're having a good start to the new year. My mother just called me upstairs to show me that water in top of tank is brown. It's still hissing(for lack of a better word). We turned the water off, but I am afraid to make it any tighter, so hopefully that's not the reason it's still hissing.. Anyway, I took a video. Is there anything that I'm missing? I would appreciate any feedback. I have provided a 28 second video if you don't mind watching.

Edit- I just checked my toilet and it is silence.. so I assume something is wrong upstairs in her toilet. AND the disregard sound in beginning..that's the closet sliding door being closed,loll....if you need a better pic/video, please let me know

Thanks a billion

:)