Thanks pooldoc.
The last pictures show the underlying concrete coming through is what it does look like.

We've never acid washed the pool....

I've informed poolco regarding the crack. I have not heard back.

What would be the way to correct the crack? From past history poolco wouldn't even pressure test lines after their consultant left the pool deadheaded.... yes they replaced pipes by filter that blew and motor but I've felt there was a small leak always that possibly was underground. Could the crack be a result of the pipes leaking under ground causing ground erosion?

How would you proceed if this was your pool? What would you at a minimum expect the poolco to do for you?