New pool owner, trying to get my chemicals balanced

[Watermom]

but I'm not sure what else could have caused it, other than not putting as much chlorine in daily or every other day in that rainy period?

Yep. That'll do it. We see it all the time. Usually it is people who come onto the forum and tell us that the rain caused their algae which isn't the case. Usually it is because people aren't as diligent about keeping tabs on their pool when it rains.

As long as you are aware and watching to keep your chlorine levels in the proper range, you'll be fine.

Hope this helps!