Looks like just a little bit of nitrogen deficiency. How far are you from finishing this plant and what kind, if any, nutes are you feeding it? Low nitrogen in the lower leaves is normal during the late stages of flowering and it's actually not a problem as too much N will stunt the flowering and leaves a bad taste in your product. As long as it doesn't move too high up the plant then don't worry about it. Looks like a really nice plant, good job! I'm doing some breeding experiments with these autoflowering strains right now and it's looking promising.
Best of luck
Joe Hemp