Could be bcos you were trying to make your voice sound deeper on the 3 weeks vid. From my experience my voice didn't stabilise until around 3 months on T when before it used to go up and down. On sime days I was pretty sure my voice sounded lower from how it had sounded the previous. But that may just be my paranoi or how I chose to talk on that particular day.
I was quite obsessive about how my voice was changing which isn't healthy. Try distracting yourself and stop making voice recordings until your voice starts to stabilise at least.