Before you get too excited, what test methods are you using?
Do you have a recent water report from the supplier?

IME, the cheaper PO4 test kits get really squirrley in the extreme ranges: upper and lower. Some just do not work much at all.
Same with NO3.

As there is no pressing issue, algae etc, I'd just keep an eye on the CO2 and routine maintenance.

The only thing might be a pH shift due to PO4 buffering.

Regards,
Tom Barr