Thanks @joekamprad
I was just thinking since it happened.
I remember that I was taking snapshots of my home folder. I have been downloading lots of stuff over the past few days and deleting them tough didn’t actually delete them as they were still there in the snapshots!
So, I went to BTRFS Assistant and removed the home snapshots and won’t be taking snapshots anymore.
Once I did that, it is back to normal and the red line is gone!
Now I have only 27% of my SSD used as compared to only 500MB free!