Low pH, Hardness, Alk, where do I start?

[ChrissyInOregon]

6/13 readings:

Alk 80
pH 7.8
Chlorine 1ppm

It has been cool here, so no one has been in the pool. We had some rain this weekend. The pool temp was down to 66, but today was up to 71. I put 4 round, approx 6ft solar cover circles on the pool on Friday (because I'm cheap and they were $3.41 each instead of $50+ for a 16ft cover). They're down to $3 now:

Intex Round Solar Pool Cover

I tested my water early evening and the pH has dropped to around 7.6, and the Alk has dropped to 70ppm. Is this from the rain, and the little bit of hose water I put in this afternoon? Should I add more borax? Baking soda? What numbers would you shoot for, and how much should I obsess about this?

The SWCG has been running 1hr/day and the chlorine is at 3ppm today.
.