Environment + Pests + Setup
This week (at day 31) I decided to end the battle against fungus gnats. Even after almost three weeks of dried-out soil, dozens of adult insects could be seen, which told me that there were pockets of moisture that I coouldn't influence. Accordingly, I went back to the original plan I had outlined earlier: bring the system into balance and use sand and nematodes. Since I should no longer have any problems with low RH, I have also reactivated the exhaust fan, which lead to the values you can see above.
Nutrients + Environment
From the outset, the plants showed a slight nitrogen deficiency, which was evident in their rather pale, light green color. This is probably due to the fact that the substrate (until now) did not contain enough moisture to allow metabolic and decomposition processes to proceed efficiently. Directly after watering I got reassured that my choice was right and the soil still alive, healthy, and ready to 'get back to work': look at those springtails!
Plants
On day 30, I topped the plants. Both had already formed three nodes and started to develop healthy side branches at all of these nodes. So, according to my plan, I removed the main shoot, leaving enough space for the stump to encapsulate without damaging the healthy plant. I also removed one shoot from each of the middle nodes, as I don't want branches that already grow towards the center (the branches will grow towards the light anyway, and this way I can ensure that there is enough air circulation and room for expansion).
Upcoming:
Start of LST