Will venture 2 guesses because you have 2 symptoms:
#1) browning / yellowing tips are often a heat problem, or moisture prob if you got them a little dry last watering or 2. Same thing actually, these 2 probs are identical in symptoms and caused by same thing...... leaves dried out a bit from dry soil or hot lights a bit hot.
#2) leaf miners causing the white strips pretty damn sure on this one.
http://www.growweedeasy.com/cannabis-leaf-miners
Neither one look like a great problem to me in your case. As they get older you are most probably going to have some shit going on.
Not sure of your fert regime but I like them a little darker and would bump up 50% for one watering but don't do anything stupid like OD them with your ferts. Just a balanced 3-1-2 fert. My plants always tend to look a bit or a lot ragged as we go deeper into flower. Look for the green, stand back 10' and if they are generally (80%) green, you are generally good to go.
Nutrient probs are difficult if not impossibe to conclusively diagnose over the internet. You'll find some kid that has a couple hours reading under his belt that will give you a chemical solution, but slow and easy at this point. No drastic changes on anything.
All in all they look decent to me, I would not me losing any sleep yet. BEST of luck. - Peace