My Implant Has Suddenly Become Hard and Larger This Morning. I've Had It for 15 Years and Believe It Was Made in Germany?

You should see a board certified plastic surgeon you can trust as soon as you can. This sounds like a seroma, hematoma or even capsular contracture.

Hematoma or seroma formation acutely 15 years after breast augmentation is extremely rare. There also some other very unusual conditions that can cause fluid to collect around the prosthesis although more insidiously. Regardless of the cause it needs to be evaluated urgently.

Sudden enlargement of a breast years after augmentation can be due to infection, seroma or sudden bleeding from a tear in the surrounding capsule. You should get checked by a Plastic surgeon as soon as reasonably possible.