Dying plants, rising PH
I have a 5 gallon tank I set up in September. I have wisteria, pennywort, anubis, moss and another big plant who's name I forget. The plants have never done very well, I've had to replace them occasionally. A good amount of the pennywort has died off starting with the stems, the big plant's leaves are slowly falling apart and now one of my Anubis plants has holes in it. About a month and a half ago I broke up a root tab into pieces and put it in my soil, didn't seem to help.
I have 7 Chili and Phoenix Rasboras, two Nerite snails and 3 generations of shrimp. They all seem to be doing fine.
For lighting I have a Finnex stingray on a timer, 7-9 hours a day with a break in the middle.
My PH has always been around 7.0, maybe a little higher. But the last few months I've noticed a week or so after a water change(I usually change about a 0.5 - 1 gallons every week or two) the PH starts rising and goes back down after a water change. None of the creatures seem to be bothered by the PH changes yet.
Up until today i've been testing my PH with test strips, just today I got a proper test kit and I found that my tap water(and tank water) is around 7.5, so I'm not sure how my tank water has ever been lower. It has me a little confused.
So my question is what should I do about the PH? I'd like it lower and more stable(assuming its changed at all and it wasn't just flaky test strips) as it is out of range for the rasboras.
My other question is what am I doing wrong with the plants?
Here are my current parameters:
Nitrate 5-10 ppm
Nitrite 0 ppm
KH 120 ppm
GH 100 ppm
Thanks in advance!