why's my pH so low??

[Doug]

Many reasons why the ph is lower than normal. First I would not worry to much at this time. Water changes are always good, but remember ro water has a low ph and some salt mixes are still under 8.0

In a mature tank the ph rises during the day when lights are on and drops during the night. Oxygen/co2 relationship, the same as fresh water. I dont assume your lighting much yet either.

Also without the specs of your system, its harder to tell. Sumps being fed from large overflows and drain pipes, greatly raise ph values. As do large skimmers.

One can also raise the ph by adding airstones, {not always the best in a salt tank}, or even powerheads, pushing water from the bottom to the surface, creating a boil.