It's hard to tell colors because of the HPS light, but potting soil with nutes do eventually run out of all the nutes. 8 weeks is more than long enough for this to have happened. Are you on a 12/12 photoperiod yet?
senorx12562 Reviewed by senorx12562 on . Yellow Leaves - PLZ help! The plant is about 8 weeks old, and there are a lot of yellow leaves. I have read that this may be a Nitrogen problem, but the soil that I am using is rich in Nitrogen. The younger leaves are usually green, but I have noticed that they are becoming more yellow as well. Temp ranges from 63-78, humidity is around 30-50%. I have a 400 watt HPS bulb about 2 feet from the top of the plant. The soil that I am using is: Miracle Grow Potting Mix (SCOTTS MIRACLE GRO 70778300 POTTING MIX+MG8QT/6 Rating: 5