Ok, 3 ladies, all in their second week of flowering, Some of the bottom leaves were turning yellow, so I up'ed their nitrogen intake and it fixed one of them, but 2 of them have leaves that are still turning yellow...

Anyone think they may know why this is???

How often are you watering and are they soil grown?

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If your growing inside, I'd bet that the lower portions of the plants aren't receiving enough light. Especially if you are pretty sure the amount of water and nutes is good.
Remember: The type/spectrum of light is FAR less important than the AMOUNT of light the girls get. Lumens is 95%, spectrum is 5%. During flowering, this may change to 90% and 10%. Still not too important!
If outside, and your sure there's no root or stem rot and no pests, I'd guess an acidic soil or lack of N or Fe (Fe not too likely). Acidic soils will lock up some of the nutes in the soil even if they are plentiful.

trying flushing that one with ph'd water and test the run off ph. itll help you know if its lockout due to ph fluctuations.

But it could just be the older leaves dying off. So i wouldnt worry unless it was spreading up the plant.

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usually when the leaves turn yellow its because of a magnesium deficiency