They're only 3 weeks old today, it's an unusual set up of which I learnt from a friend, very surprising this method, if your confused as to the layout.. I use a recirculating system with rock wool cubes and resovoir with 3 part nutri thrive and a small am out of root accelerator ..does anyone know what it could be? It's traveling fast up 1 of 6 that are on this system.. hasn't affected any of the others.. :/