First time Hydro-DWC-Mars Hydro

Hello people, this is my first attempt at hydroponics. Tomorrow the babies' heads will come out. As soon as the first roots come through, I place the rockwool cube in the middle of the clay pebble. The DWC system from Marshydro has a top feed so the seedling is supplied with enough water until the roots reach the water. The first nutrient solution I made has a slightly higher EC than shown in the picture. It will be difficult to keep the nutrient solution at 20 degrees Celsius but I'll see ^^ I use the complete Cannaaqua line. I soaked the rockwool cube for 24 hours in a pH-adjusted solution so that it had the correct PH value in the rockwool cube. I also soaked this with Canna Start for three hours. If you have any tips or questions, get in touch!! Both seeds came. However, they don't look so healthy. The Gorilla Cookie only had 1 cotyledon from the start. I'm giving it a few days now and if it grows too slowly I plant a nine seed. Maybe I put them in the DWC system too early... Well, that's just how you learn ^^ The EC rose from 0.9 to 1.2 after 4 days. I think that's normal, the clay pebbles also increase it as far as I know.