Fish seem healthy, though I did lose another this week. But she had been swimming straight at the airstone for a while, so I suspected she wasn't going to make it.
I've removed all of the aquarium gravel, and put in the last of my clay, in the hopes of having a surface to help filter the detritus without raising pH:
I also removed all of the rockwool today, transplanting those plants directly into the clay. I also transplanted the seedlings I'd started a few weeks ago. The growbeds now have about as many plants as they'll be able to fit in, once the plants get bigger:
pH remains stable at 8.1, though I am treating with small daily doses of acid. Perhaps with all the rockwool and gravel gone, it will start to lower.
Nitrates, nitrites and ammonia are good. Water is still awfully hard, but that'll clear up in time.