Our daughter didn't X until Y. Today she's fine. I was slow in math, then I got a degree in it. We have two kids, both in college. The milestones don't matter

Our daughter didn't X until Y. Today she's fine. I was slow in math, then I got a degree in it. We have two kids, both in college. The milestones don't matter unless they are a true diagnostic indicator of something wrong. Yes we stressed over the milestones anyway. You will too. That's as normal as everything else you're experiencing. It's worse if you know other parents, because then you'll start comparing. Don't do that. Straightforward fatigue could be part of what you're experiencing, so you should try not to blame yourselves. A thought that occurs to me is that the brain is to a large extent self organizing, and also making up a lot of its own stimuli. It is not a function that produces certain outputs upon certain inputs. There are no specs, no unit tests, no code coverage, the code is not human readable, there is no diff. Your daughter is doing most of what's important.