yellow leaves;
1) too much water?
2) not enough nitrogen
3) iron or other micro nutrient deficiency

Yellowing leaves from the bottom up is normal for indoor grow as the plants use up the nitrogen in the medium. Growers don't replenish toward the final bloom phase as the green leaves do not help with the bud growth and taste. The same could be said for outdoors in a container. Usually in the earth they plants don't yellow until very late, if the do at all.