Yellow ends on leaves?????? - HELP!!

hey all!, just noticed a few of the leaves near the top are yellowing at the ends the light is at least 17" from the plant so dont think there burning?? so anyother surrgestions?
Thanks

im having the same problem, could it be nute related? i fed them yesterday and no improvement 24 hours later. not really a big problem yet (the yellowing is only on the newer leaves, on the tips).

i would say yellowing or browing on the top of the plant at the tips would have to be burn of some sort. pics would help?