I probably should just keep my mouth shut at this point, this statement will stir up lots of fuss. You might as well trim those bottom leaves off, they tend to be more of a drain on the plant at the stage they are in. I am a firm believer in trimming, most of your nuteriants come from the roots and the younger leaves are more active with the light than the older. When you trim off the older leaves you will accelerate the growth of the younger and you have the root system already in place to handle the accelerated growth of the leaves. The roots will keep pumping the food to the older leaves as long as they are there. You can always try this on one plant and keep a close watch and see the difference between trimming and not trimming.