I would guess that is a magnesium deficiency..looks like that baby is about 3-4 weeks from harvest....the plant is using all of it's energy to produce that fat bud...try some natural guano tea (ratio lean towards phosphorous) mixed with some MaxiCrop or other seeeweed/kelp based addiditive....not too strong a mix...

Overall...I would not be too bothered..I will always cut those leaves off the plant (leave about 1/2 inch from the stem...the fan leaves are always the first to go...

looks like a nice indica....good luck