Thanks for the reply. I am not too worried about the fires for myself, since I live in the flatlands away from the forests. I am more sad about the people who had their homes destroyed or some of the state parks that got burned down. The good news is that a lot of the old redwood trees are "used to fires" so they survived and it gives their seeds a chance to sprout. Mainly the problem for me is the bad air that has lingered here for about a month now.
So regarding my tank, I haven't added or removed anything, so I still think the slight pH rise is due to substrate wearing out. I'm not that worried about the actual pH, but wonder what has changed about this tank over the last few months. I think the first half year or so everything was great. But sometimes around the summer (may / june) it would start getting stretches of "bad days" where the shrimp would just quietly stand around. Those periods seemed to come and go, but the problem is worse now. I suspect, but can't prove, that it's something that is coming in thru the air, since the first time it happened my neighbor was having a BBQ and my room was smelling a little bit smoky. The other times it happens I can't trace it to doing anything, except maybe the room was warm and I was running the air conditioner or fan.
So since I can't find any cause, the only thing I can try doing is water changes. I also turned off the air stone, but I do have a little device that lets one bubble per second into my water pump so there is always a small stream of bubbles. I also added a Sotching oxydator, but it only seems to bubble with the lights on.
I had some other idea, which is that the biological balance of this tank became "off" somehow. Like there is not enough or the right kind of biofilm. Maybe the first batch of babies were very hungry and ate all of it away, or I might have nuked it with the H2O2 treatments. I started dosing small amounts of fertilizer since some of the plants were getting holes in the leaves anyway. Maybe I should also dose nitrifying bacteria, or some of that probiotic bacteria? Oh, I had also reduced lighting at some point to prevent hair algae, so maybe time to add more again?
That one shrimp's antenna seem to be getting a tiny bit shorter every day, although still active and grazing around. But it is probably doomed to the same fate as the others unless I find a better treatment. Poor guy.
But in other tank news, my old and neglected Amano tank with the overgrown moss wad seems to be doing well. I moved one of my juvies there in June as a test, and that shrimp is thriving. It happily grazes the moss every day and grew up quickly to a large size. The juvies in my tank with the problems seem to grow up much slower. I'm trying to figure out what really are the differences between these two tanks, but that is a topic for another day.