Literally what happened to me. I run and lift weights multiple times a week. Just getting older I guess.
Discussion
You can be strong and still have shitty posture. I should know.
https://www.amazon.com/Treat-Your-Back-Robin-McKenzie/dp/0987650408
If you can keep your discs aligned into your 60s, they will crystalize that way and you'll be ok for the rest of your life as long as you don't do anything crazy.