Generally speaking, low pH tanks mean that there's a buffering substrate. Not always, but most often.
Not only that, but it's a Fluval aquarium... I had guessed that *maybe* the tank came as a kit... and had Fluval Stratum. Although, looking at the kits, I see it doesn't come with gravel! LOL
Once the soil exhausts itself (and Fluval doesn't have a good rep when it comes to longevity or buffering ability...), then yes, your pH would rise. I am seeing more and more that Fluval is buffering to a lower pH so maybe they changed something about the substrate?
Even if it's exhausted, it would still be good for your plants, so no worries there!
As far as the shrimp goes... you honestly might be fine! You might not have any issues! However, if you have problems with the shrimp each time you do a water change (not necessarily during, but within days of), then you might want to consider if anything needs to change.
I was more curious about the KH of tap vs tank - after the tank has settled for at least a few days or so after a water change.