Ok my reservoir is changed every 6-7 days also no light gets to the reservoir,I'm using ecolizer nutes on nft table using Rockwall cubes on spreader mats, the plants are 4 weeks into veg and were cuttings from some very healthy and nearly harvested cheese plants which were grown in biobizz all mix , I'm on 2 x 400 superveg lamps temp is fine humidity does sometimes slump to around 30% but generally picks up, but the colour of the roots appear to be brown in colour and have also taken a while to appear?