Still very small... but the cube are small too, there were little white roots (not a lot) on the bottom and side. As the plastic container was larger I was afraid they got some direct light.
Also... I had a fail with the heating control and temperature jumped at 32º for 8h during the night! The rock wool cubes dried and hope they didn't suffer to much stress.
23/01/2022: no grow... don't get why it's so slow.
Note: the nutrients in power are expressed in g/L (not ml/L). I have to say I'm not pretty convinced but still give a try with those kind of nutrients.
I have the "chance" to get a water at home with pH 7 and Ec 0.05, pretty much a free osmosis treatment!