I'm growing micro arugula, nft hydro system under T5 blue lite. Seems as it gets to about 5 to 7 days old a lot of the leaves lighten up to almost a yellow color. Any ideas here? The younger stuff is so much greener. My food is at 1900 ppm, ph around 6. The seeds were sown in burlap and sit in metal trays. I'm thinking a possible chemical reaction from the metal trays and the nutrient combination.

thanks for reading this,

J