You have big buds like that and no frost? Am I seeing that right, the bottom is green and the tops are yellow? Are you hand watering? How much coir are you growing in?

Every medium needs to be given plain water every now and then(aka flush). From what I have read about coir is suppose to be the shit. But, I dont think you could go a whole grow without ever flushing, salts build-up way to easily. The way I see the picture though it looks like an immobile element lock-out possibly Fe(iron). The problems are probably occuring from an incorrect ph.

Ph and ppm(ec) readings of fert mix would help.