The plants have been at a complete standstill in terms of growth for a few weeks now, as the temperatures this summer have been catastrophic.
We have now moved the light cycle to the night and got a new longer air supply hose so that we can draw in cooler air.
We had temperatures of 35°, which is simply far too high. Now we're at around 30° and you can see that the plants are already doing better. We are still a long way from the perfect 27°, but the humidity is high enough to provide the right VPD.