Trim Yellow Fan Leaves?

I'm in 3rd week of flowering 3 nirvana white widows. I wanted to see how long I could go in between feedings before they started showing deficiency (about 7 days). Now a few of my bottom fan leaves are yellow and I was wondering if I should cut these off or leave them. I mean are they still processing the light or are they now detrimental to the progress of my plants? I've already trimmed off so many bottom fan leaves up to this point (for the purpose of light penetration using 250 watt hps) that I didn't know if I should trim any more. But if these yellow leaves are useless now there's no need to keep them intact right? These things are about 26 inches and they are pretty branchy and certainly have no shortage of leaves.

why would you stress them in thier most vulnerable stage? watch for hermie`s
the leaves will fall on thier own. they are kind of useless that far away from the light so if you did want to trim them only 20 % at a time. and let them recover before doing it again