The new tower and the pcb are being tested for 2 weeks now. Everything is working great.

On the picture you can see a 3 weeks old basil plant, with 2 weeks in the tower. You can also see the fog coming out of the tower. The roots are growing and are white, which is perfect. The watering cycle is 10 min ON with 1 mister and 5 min OFF.

The solution was at 1 EC during the 2 weeks I just adjusted it to 1.5 EC. 

As the prototype PCB is working and the circuits of the different sensors are operational (pH, EC, Temperature), I just ordered a PCB with all the components. I am waiting for the delivery to be able to test it.