FastBuds/Rockwool

You can use only the little cubes in the first week of germination, it's easy to control the water content in the rockwool. then I transfer to the large cube when the roots are already at the bottom. At that moment the plant doesn't drink too much water, you have to be carefull because the rockwoool cube holds too much water for a seedling. You can check my recent diaries to see what i'm talking. After the transplant the plant will be good with 10-15 days without more water, only when the cube gets lighter. Some time to time the rockwool will need a reset because it will be hydrofobic (in flower I do this once per week, in veg I do this on 3rd or 4th week) fully soake the rockwool a let a 20-30% runnoff, don't do that in a single time, If you put 1 liter on a dry cube it will runnof but the cube is not fully saturated, give 20-30 minutes between small feeds (like 250ml), after 2 or 3 small feeds give them a good runnof. I think you are feeding too much water IMO, or the cube aren't holding the water (reset needed) or you are not leting dry back. Maybe the lower humidity has to do with that but in this stage one good feed should last you around 7-10 days.

For the stage of growth you are in no. The seedling needs to build a root system. You want to have the block dry out to about 40% moisture. Then do feed shots around 100ml till you hit 80% moisture content of the block. There is no need to feed to runoff at the early stages of growth its all about root building. After there is a root system throughout the block you can start to feed to runoff. Typical runoff would be around 10-15%. Just a slight adjustment on what you are doing already.

High, Rockwool is only great for feeding from the bottom like in a Ebb and Flow system. You want to lift them of the ground a bit because otherwise the roots will be one big ball at the bottom of the cube. You want to let them dry out in between waterings. They really do suck up a lot of moist and will be full with algea if you do not let them dry in between. In my opinion it is not the best medium to use. But if you want to give it a try then water from the bottom. I did have great results in the past with the GHE Tripart nutrients with their Cal-Mag supplement and pH minus. Feed only the bottom 10% from the cube and it will suck up the moist like a wick and in a minute the bottom 20% will be saturated. Happy Growing and keep the toe showing! 💚