We have to try to lower the CO2 concentrations.
The producers of CO2 are: Bacteria, fish, mushrooms, people.
Uptake of CO2: plants, algae.
The tanks are well aerated. The surplus CO2 should evaporate and get back to natural values (Yellow part of the pH KH CO2 table).
I think the easyest step is removing the mushrooms and see if it improves.
You could also try lighting the tanks to grow some algae. Unfortunately the catfish won't like the light.
We could place some large plants in the tent.
We have to check the growbeds to see if something is rotting/decaying.
Perhaps we could place the air pumps outside the tower, so low CO2-air flows through.
It is a good idea to feed sparingly, bacterial CO2 production will diminish.