What I'm seeing is lighter colored growing points. Sometimes this is from fast growth — plants don't form chlorophyll until they're hit by light. If the plant is having a growth spurt, sometimes the chlorophyll production lags.
Sometimes it's from a micronutrient deficiency or lockout. If it's lockout, it's often from pH, but it could also be from an over-abundance of something like calcium. I hate to tell someone to try and change the chemistry of their soil, as this is a difficult thing. You could do a few foliar sprays with a nute containing iron and zinc, without causing problems. But as I said, this might be nothing.
