I know this is kind of old but I wanted to explain this. When I was younger I used to read a lot and play a lot of video games. This was before every game had voice acting so you had to read all the text to know what was going on. I didn’t have any problems pronouncing words because I was constantly expanding my vocabulary. Once you get adulthood though things kind of get routine. You go to work/relax on the weekend/repeat. You don’t have time to practice your old hobbies that you used to and you stop meeting new people as often. Your vocabulary slowly changes to match those around you and that work environment. It happens to all of us, and it will most likely happen to you too.