Será uma deficiência de cobre?

Aside from raising lights you can reduce the time the light is on. You can try low stress training as well. You can reduce your amount of nutrients some, in case some of the color difference is partially due to over fertilization. I would increase cal-mag still as I said before. It can affect the plants ability to produce enough chlorophyll if they don't have enough cal-mag with high intensity lighting. Adding CO2 can help the plant function at a higher light intensity with extra cal-mag than usual as well. That's what I found in my research and experience. Good luck on your first grow Bud!