nothing I learned in any of my physics courses dealt with fossils, geology, or radioactive decay.
You clearly didn't take much physics. Even third semester physics for non-majors covers radioactive decay. And the related physics don't look good for a young Earth.
As I said, radioactive decay, and all information regarding atoms, was covered in Chemistry, not Physics. If that has changed recently, I wouldn’t know about it, but that’s how it was when I went to school.