Mate, if they're Auto's, there's not much you can do right now & Nitrogen won't fix the problem. In fact, probably not a good idea right now if that's the case.
If they're photoperiod plants, then they should still be responding to the increasing light-levels with increased vegetative growth & not changing colour (unless you're under-feeding them) until the natural light levels decrease & they naturally go into flower, but that's unlikely until mid-January.
I'm sure the cogniscenti will give me a jolly-good spanking if I'm talking through my arse here......
As they say in the classics, "A picture is worth a thousand words".......