If I'm reading it right, the product page says those fans are PWM. From your first image, it shows that channel is not controlled via PWM but voltage controlled. Might want to switch that to PWM.
There are nothing connected to channel 2 atm, as nether the 3-pin pump (Laing DDC-pump 12V DDC 3.25 18W) or the fans worked on it. Regardless of settings (at least the once I found).
Even tried to switch around the cables, to see if that was the problem.