Can anyone tell me if these lower yellow leaves are a sign of anything??? I've been veggin them w/24 hr light but have reduced to 20hrs with natural light and unnatural light in a 2' wide 3' deep 2' tall space using a sinlge 37watt CFL. no nutes added. watering when soil is dry to an Inch deep. all are in 4" round peat pots. Thanks for any help!!!