I agree with everyone here who says you’re doing great!
Classes do get harder, and I can share that our Jr just got an 80 on a phys test and 85 on a math test. And, he’s a math/science kid! (in phys C, multivariable calc). Depending on how your teachers grade, one mistake in the middle of a problem makes the rest of the problem wrong and can result in 20pts off. I wasn’t a math/science major, but I’m imagining this reflects college grading.
For any classes where you get below what you’re shooting for, go into the teacher and get extra help. For physics, look at Kahn academy videos too (though that didn’t help our S on this past test, but class average was 70) and look at how you’re doing vs class average to put your grades into perspective.
Our S was upset too. But, these are life lessons so use them to build the skills to succeed in college and beyond.