Why are your temps and humidity so low plants look droopy and why you using low doses of Cyco Nutrients you should be using 8 ml per gallon by now should at least be in the 500-600 ppm range good nutrients if used correctly
@THESTONEDCHEF, The temperatures are in Celsius degrees not Kelvin. In Western Europe, right now, it's winter. So 20° Celsius doesn't seem low to me.
The indoor air is dry because of my heating method (wood) which produces a lot of dry air. The outside air is also dry because of the frosts in the morning. I would like it to be a little more wet but I can't help it.
Here the tap water here is already over 550ppm without any nutrients. More generally, with fertilizers it is easier to add than to remove. I don't trust much what the manufacturer, Cyco, recommends on its bottle.