What nutrients, ph, and ppm?

Again im not a fan of rockwool due to the extreme uptake of water. The plants look healthy but there should be more roots for sure. Maybe try a string touching water similar to a wich system to only dampen the lower area of the plug.

The area in between the bottom of the rockwool and water might be too dry from the heat To let the roots spread the gap?

Just zoomed in on the root pic...did you cut the whole way through the Styrofoam or just enough for the plug to set into it....if you didn't cut the whole way through you need to. That Styrofoam is closed cell and will only let root growth through the air gap in between the cells And not like sponge/rockwool Grow through the open cells.

I installed a bluelab guardian monitor and found out my ph was nearly 2. I adjusted it to 6 and within a few days new healthy roots started popping through and after a few more they look like so. Incorrect ph level mainly caused my root issue. I did add some room fans to lower the temp, but that was a few weeks prior to adjusting ph levels