My pH used to tank because we had super soft city water (as soft as you can get) and with my plants after a week it would drop significantly. My fish were never affected, maybe because it happened slowly over time, but I'm wondering if you might be getting some pH swings? I ended up having to add crushed coral to my filter which stabilized it.
I'd maybe check tap pH, tap pH after sitting for a day, tank pH after a WC, and tank pH right before a WC. Just a thought.
I did 50-75% WCs every week with zero issues ever.
I would also just check the water temp before a change with a thermometer vs your hand JUST to take that out of the equation. It's free.
I hope you can sleuth this one out!
Good suggestions, I'll give those all a try.



